Air Conditioning Audi A8 D2

A/C refrigerant system (R-134a), safety measures

1. The subassemblies and lines of the air conditioner are filled with tetrafluoroethane also known as refrigerant R-134a.
2. Refrigerant R-134a replaces the refrigerant R-12 which is reported to have harmful effects on the earth's ozone layer.
3. R-134a and R-12 systems are similar in design but there are very important differences in the refrigerants, lubricating oils, service equipment and A/C system components.

If liquid refrigerant has come in contact with your skin or eyes

1. Do not rub skin or eyes
2. Immediately flush with cool water for 15 minutes
3. Rush to a doctor or hospital
4. Do not attempt to treat yourself

A/C refrigerant system, general repair guidelines

The refrigerant circuit of the air conditioning system must not be drained and opened (See A/C REFRIGERANT SYSTEM (R-134A), SAFETY MEASURES ) unless this is necessary because of safety precautions or unless components of the refrigerant circuit of the air conditioning system have to be replaced.

When performing all other usual vehicle repair work, the refrigerant circuit of the air conditioning system should also remain closed.

Servicing operations which can be performed on the heating and air conditioning system without opening the refrigerant circuit, are described in A/C SYSTEM REFRIGERANT SYSTEM, SERVICING .

Note. The connections for switches mentioned in this Repair Manual are provided with a valve which closes automatically when the switches are unscrewed. These switches can thus be replaced even though the refrigerant circuit is fully charged.

For servicing operations to A/C system that require discharging the refrigerant circuit. See A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING .

Commercial designation

Obtain R-134a refrigerant (tetrafluoroethane) from a local A/C supplier under one of the following names

1. H-FKW 134a
2. SUVA(R) 134a
3. KLEA 134a

Note. R-134a refrigerant is packaged in different containers. Use only R-134a that comes in containers having correct types of service fitting.

Color

Refrigerant R-134a is colorless and is invisible as a gas. Only the layer between gas and fluid is visible (fluid level in tube of cylinder or bubbles in sight glass in fluid reservoir.) R-134a when viewed through a sight glass (if installed) may appear milky due to the mixing of refrigerant and lubricating oil (PAG oil).

Airborne properties

Escaped refrigerant gases are heavier than air and will gather first in low places, like under the car. R-134a refrigerant gas displaces oxygen and may cause suffocation in low areas of poor air circulation.

Solubility of refrigerant oil

A required special refrigerant oil Polyalkylene Glycol (PAG) synthetic oil is used to lubricate cylinder walls and bearings and enters the refrigerant circuit to some degree. This oil is NOT compatible with mineral based oils used in R-12 systems.

Note. R12 refrigerant systems use mineral oils which are not dissolved by R-134a refrigerant and are unusable.

Effects on the environment

Because R-134a does not contain chlorine atoms, the major catalyst in ozone depletion, R-134a has no ozone depletion potential.

R-134a does not cause smog and has a considerably lower global warming potential (greenhouse effect) than R-12 refrigerant. Nonetheless, do not release R-134a into the environment and always recover/recycle using approved service equipment.

Toxicity

Refrigerant R-134a is non-toxic up to a temperature of 101°C (214°F) and is safe when handled and used properly.

Above 101°C (214°F), gas pressure is above 39.5 bar (573 psi) and R-134a begins to decompose into poisonous gases (hydrogen fluoride, carbonyl fluoride and fluorine). These gases give adequate warning of their presence since they cause irritation of the mucous membrane (throat).

Refrigerant R-134a gas has no effect on foodstuffs; it does not poison food or make it inedible.

Temperature/pressure relationship

In a not fully charged refrigerant container, refrigerant gas comes to the surface which under particle formation becomes fluid. This occurs under pressure and is know as gas pressure. Similar to R-12 refrigerant, the gas pressure of R-134a is temperature dependent.

TEMPERATURE\PRESSURE RELATIONSHIP

1. While performing body/paint repairs involving the use of preheating or drying ovens, do not expose any component of A/C system to temperatures above 80°C/176°F.
2. Excessive heat will cause a pressure increase which could burst the system.
3. Temperature/pressure chart. See «A/C REFRIGERANT SYSTEM (R-134A), PRESSURE & TEMPERATURE RELATIONSHIPS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-pressure) .

Effects on plastics

Refrigerant R-134a will deteriorate some plastics. When system temperature drops, these plastics can be deposited at the expansion valve or restrictor causing blockage. Therefore, when making system repairs, use only genuine Audi replacement parts which are specified for use with R-134a refrigerant.

Effects on metal

In its pure state, refrigerant R-134a is chemically stable and will not attack iron or aluminum. However, the mixture of R-134a and PAG oil may deteriorate certain metals (copper) which could lead to blockage, leaks or deposits on the compressor piston. Therefore, when making system repairs, use only genuine Audi replacement parts which are specified for use with R-134a refrigerant.

Critical temperature/critical pressure

R-134a refrigerant will remain chemically stable up to a pressure of 39.5 bar (573 psi). This corresponds to a temperature of 110°C (230°F). Above this temperature the refrigerant deteriorates (see flammability).

Water solubility

Liquid R-134a refrigerant will absorb only very minute quantities of moisture. However, R-134a vapor can absorb large amounts of moisture.

Water in the system forms ice in the expansion valve or restrictor causing the system to stop cooling. In addition, moisture combines with the refrigerant to form acids which will damage the system.

Flammability

R-134a refrigerant is not flammable. In fact, it tends to inhibit combustion and has a fire extinguishing effect. However, a flame or glowing hot surface, as well as ultraviolet light (from electric welding), will decompose the refrigerant into poisonous gases (hydrogen fluoride, carbonyl fluoride and fluorine). These gases give adequate warning of their presence since they cause irritation of the mucous membrane (throat).

R-134a can become flammable at pressures above ambient pressure in conjunction with air concentrations greater than 60% by volume.

Refrigerant containers

There must be pressure space available in the fluid area of the container. At increasing temperatures the fluid expands, the space filled with vapor becoming smaller. At a specific point there will only be fluid in the container. Beyond this point, only a slight increase in temperature will result in a very high pressure in the container.

Without sufficient room for expansion of R-134a (gas cushion), the container could explode when the temperature rises causing serious injury.

DO NOT exceed maximum rated capacity of refrigerant containers. Never fill a container to more than 60% of its gross weight rating (for example, 18 lb in a 30 lb container.)

Leak detection

Use halogen leak detector Hitec HI400A-TEL, or equivalent, to check for R-134a system leaks. This tool can also be used to detect leaks in R-12 systems. Many currently available R-12 leak detectors cannot detect R-134a refrigerant leaks.

A/C refrigerant oil (PAG), properties

A special Polyalkylene Glycol (PAG) synthetic oil is used in R-134a systems. This oil is NOT compatible with mineral based oils used in R-12 systems. See safety measures under A/C REFRIGERANT SYSTEM (R-134A), SAFETY MEASURES for Warnings and Cautions regarding proper oil usage.

Refrigerant system with restrictor and accumulator

1. Compressor
2. Condenser
3. Restrictor
4. Evaporator
5. Accumulator

Scheme 1

Note. Arrows indicate direction of refrigerant flow.

A/C compressor

The compressor is driven via a belt on the engine when the A/C clutch engages (A/C ON).

Low pressure refrigerant gas from the evaporator is compressed by the compressor. After compression, the refrigerant gas (now high pressure) flows to the condenser.

The variable displacement A/C compressor varies piston stroke and output depending on load requirements and suction pressure.

Note. The compressor contains PAG type refrigerant oil that is mixable under all temperatures with refrigerant R-134a. A label on the compressor indicates that compressor is for R-134a systems only.

Scheme 2

A/C condenser

The condenser transfers heat from the compressed refrigerant gas to the outside air which causes the refrigerant to change state from a gas to a liquid.

Scheme 3

Note. Illustration shows the condenser from an Audi 100 model.

Evaporator

Liquid refrigerant entering the evaporator absorbs heat from air passing through the evaporator fins and cools the air. As the refrigerant absorbs heat it turns to vapor and is suctioned by the compressor.

Scheme 4

Note. Illustration shows the evaporator from an Audi 90 model.

Accumulator

The accumulator traps the mixture of refrigerant vapor and gas coming from the evaporator. While in the accumulator, the refrigerant vapor turns to gas and, along with the refrigerant oil, is then suctioned by the compressor.

An oil extraction passage is incorporated into the accumulator to ensure that refrigerant oil flowing with the refrigerant does not remain in the accumulator.

Any moisture in the system is absorbed by the desiccant in the accumulator.

Scheme 5

Note. Do not remove caps -A- and -B- until ready to install new accumulator. If caps are removed too soon, the desiccant becomes saturated with moisture after a very short time. If this occurs, the accumulator must be replaced.

Restrictor

The restrictor restricts and controls refrigerant flow to the evaporator thus lowering refrigerant temperature and pressure.

Upstream of the restrictor, the refrigerant is hot and under high pressure. Downstream of the restrictor, the refrigerant is cold and under low pressure.

A strainer located upstream of the restrictor filters out any dirt or particles. Another strainer located downstream of the restrictor atomizes the refrigerant before it enters the evaporator.

Note. Insert restrictor so that arrow -A- points to evaporator. Illustration shows the evaporator from an Audi 90 model.

Scheme 6

O-rings

O-rings seal the connections between components of the A/C system.

Use only O-rings which are compatible with R-134a refrigerant and refrigerant (PAG) oil. Refer to the most recent parts information when obtaining new O-rings. O-rings are recognized by colors (currently red, green or violet).

Scheme 7

Note. Handle O-rings only in a clean working environment. Do not reuse O-rings, always replace. Always use correct size O-rings (dimensions -a- and -b-). Lubricate O-rings with refrigerant (PAG) oil before installing. Always make sure to properly install O-rings on line/component mounting flanges/grooves. O-ring and torque specifications also apply to threaded connections in the A/C lines.

Hoses and lines

The mixture of refrigerant oil (PAG oil) and refrigerant R-134a attacks some metals and alloys (for example, copper) and breaks down certain hose material. Use only hoses and lines which are identified with the lettering "R-134a."

Hoses and lines are secured with threaded connections. Always properly torque hose and line connections.

A/C refrigerant system (R-134a), valves and switches

Note. Check shift pressures, switch and sensor removing and installing, as well as switch locations in refrigerant circuit. See A/C SYSTEM REFRIGERANT SYSTEM, SERVICING . There are several different versions of switch and sensor. See A/C SYSTEM REFRIGERANT SYSTEM, SERVICING .

Pressure relief valve

The pressure relief valve is mounted on the compressor. At approx. 38 bar (551 psi), the valve opens to vent excessive pressure. When system pressure is reduced to approx. 30-35 bar (435-508 psi), the valve closes to prevent total refrigerant loss. The refrigerant will not run out completely.

Scheme 8

Function

Switches A/C clutch -N25- OFF if system suction pressure is too low (low refrigerant charge). This switch protects the compressor if the refrigerant system is empty.

Scheme 9

A/C refrigerant high pressure switches -F23- and -F118

Both switches are incorporated into a single housing.

Function of -F23

Switches coolant fan -V7- to second speed when A/C system pressure increases.

Function of -F118

Switches A/C clutch -N25- OFF if system pressure is too high.

Note. The illustration shows switch from Audi A4.

Scheme 10

Valve connections for pressure switches

Schrader valves installed under A/C system pressure switches allow switch replacement without discharging refrigerant system.

Scheme 11

1. A/C system low and high pressure switches use different threads.
2. Use only the correct switches and O-rings specified for use with R-134a refrigerant and PAG oil. See «A/C SYSTEM REFRIGERANT SYSTEM, SERVICING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-system-refrigerant-system-servicing) .

1. Switch connection
2. O-ring
3. Schrader valve insert

Note. Always refer to the latest parts information to ensure correct switch application.

Connections for quick coupling adapter on refrigerant circuit

Note. Use only the specified quick coupling connectors resistant to R-134a and respective refrigerant oils. Different connections for the high and low pressure sides (outside diameter). Before removing the valve or valve inserts, discharge refrigerant system. See A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING . Always reinstall cap over service valve (with sealant). Location in refrigerant circuit. See A/C SYSTEM REFRIGERANT SYSTEM, SERVICING .

High pressure service connection with Schrader valve

1. Service valve connection (soldered)
2. Schrader valve insert
3. O-ring
4. Cap with seal

Scheme 12

Note. Only a high pressure service valve is used for A/C system servicing. A low pressure service valve is not installed in the A/C system. Perform all A/C system service operations (i.e. discharging, evacuating, and charging) through the high pressure service valve only. Before removing the valve insert from the high pressure service valve, discharge refrigerant system. See A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING .

A/C refrigerant system (R-134a), pressure & temperature relationships

The pressures and temperatures in the A/C refrigerant system vary depending on engine speed (RPM), coolant fan speed 1, 2 or 3, engine temperature, A/C compressor (ON/OFF), outside temperature, humidity, required cooling performance, etc.

Pressure and temperature specifications given in (Scheme 14) are based on the following

1. Engine running for approx. 20 minutes 9 (operating temperature)
2. Engine speed (RPM) 1500-2000
3. Outside (ambient) temperature 20°C (68°F)
4. With the engine not running and the ambient temperature at 20°C (68°F) the pressure in the system should be approx. 4.7 bar (68 psi). For properties of refrigerant R-134a, see «A/C REFRIGERANT R-134A, PROPERTIES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .

Scheme 13

Refrigerant circuit with restrictor and accumulator

HD = High-pressure side

ND = Low-pressure side

Note. Small -arrows- indicate direction of refrigerant flow. Low side pressures are regulated and maintained within certain tolerances by the variable displacement compressor independent of compressor speed. See A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES , refrigerant system pressure testing.

1. A/C compressor, high pressure side
2. A/C condenser
3. Restrictor
4. Evaporator
5. Accumulator
6. A/C compressor, low pressure side

1. (Scheme 13)on for component identification.

Scheme 14

Contact corrosion!

With the extensive use of aluminum construction, corrosion caused by contact between dissimilar metals may result if the wrong fastening components (screws, bolts, nuts, washers, rivets, plugs, grommets, adhesives, etc.) are installed.

For this reason, the manufacturer only installs fastening components that have a special surface coating, recognized by its greenish color, and only uses rubber parts, plastic parts and adhesives that are electrically non-conductive.

These parts, compatible for use with aluminum, are also available as replacement parts.

Use only Genuine Parts!

If there is any doubt about whether the old parts are suitable for re-use, always install new replacement parts.

All accessories must be approved by Audi of America, Inc.

Damage from contact corrosion caused by improper assembly with unsuitable parts is NOT covered under warranty!

A/C system refrigerant system, servicing

Note. A/C system components identified with an asterisk (*) may only be serviced or replaced after properly discharging refrigerant system. A/C system components not identified with an asterisk (*) can be serviced or replaced without discharging refrigerant system.

HD = High-pressure side

ND = Low-pressure side

Note. The following list refers to items in (Scheme 15).

1. Compressor* Removing and installing compressor from mounting bracket. See «A/C COMPRESSOR FROM MOUNTING BRACKET, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-compressor-from-mounting-bracket-removing) . Manufacturer Nippondenso NOTE: Removing and installing ribbed V-belt: See «RIBBED BELT, REMOVING AND INSTALLING»(ref-196865-S24437602202005100900000) .
2. A/C compressor speed sensor -G111-* Not applicable for Nippondenso compressor
3. A/C clutch -N25- Testing. See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__output-diagnostic-test-mode-dtm-function) . Servicing. See «A/C CLUTCH, SERVICING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) Check and adjust gap between belt and clutch disc. See «A/C CLUTCH, SERVICING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . Removing and installing ribbed V-belt See «RIBBED BELT, REMOVING AND INSTALLING»(ref-196865-S24437602202005100900000) .
4. Oil drain plug*
5. Pressure relief valve*
6. Connection with valve*
7. A/C refrigerant pressure switches -F23-, -F118- and -F129- Function, removing and installing. See «A/C REFRIGERANT HIGH PRESSURE SWITCHES -F23- AND -F118»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . A/C pressure switch - F129-, function, removing and installing. See «A/C PRESSURE SWITCH -F129-, FUNCTIONS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-pressure-switch-f129-functions) . NOTE: A/C refrigerant high pressure switch -F23- and A/C refrigerant high pressure switch -F118- are installed on vehicles with an A/C control headup to Part No. index letter "H." On vehicles with an A/C control head beginning at Part No. index letter "J" A/C pressure switch -F129- is installed (introduction of sensor for air quality -G238-).
8. Condenser*
9. Cap With seal, always re-install after servicing
10. Service valve (high pressure)* At condenser
11. Coupling in refrigerant line*
12. Restrictor*
13. Evaporator*
14. A/C refrigerant low-pressure switch -F73- Function, removing and installing. See «A/C REFRIGERANT LOW PRESSURE SWITCH -F73»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . Deleted with introduction of A/C pressure switch - F129
15. Connection with valve* For vehicles without A/C refrigerant low pressure switch -F73- a cap with seal must be screwed onto the connector for this switch
16. Accumulator*
17. Cap Not applicable for Nippondenso compressor
18. Connection with valve* Not applicable for Nippondenso compressor

Scheme 15

Switch -F23

Switches radiator coolant fan -V7- to stage 2 (terminals 1 and 2 in connector -B-). (Scheme 16)

Scheme 16

Switching pressures

1. Fan stage 2 on (switch closes) 14.3 up to 17.3 bar pressure
2. Fan stage 2 off (switch opens) 10.9 up to 15.3 bar pressure

Pressure difference between switching points: 2.0 up to 3.4 bar

Switch -F118

Switches the compressor off via the A/C control head -E87- in the event of overpressure in refrigerant system (terminals 3 and 4 in connector -B-). (Scheme 16)

Switching pressures

1. Compressor off (switch opens) 28.2 up to 31.0 bar pressure
2. Compressor on (switch closes) 11.5 up to 15.0 bar pressure

Removing and installing

1. Remove bumper See «BUMPER»(/audi/a8/d2-1994-1999/remont/exterior-body-panels/#bumper) .
2. Separate plug connection -B-.
3. Replace O-ring -A- (7.6 x 1.8 mm). Tightening torque: 5 Nm (44 in. lb)

Scheme 17

Note. To test the A/C system cooling performance, plug the removed switch back into wiring harness. The refrigerant system remains closed due to the Schrader valve. Illustration shows switch on Audi A4.

1. Switches A/C compressor off in the event of pressure drop in refrigerant system (protects compressor when circuit empty).

Switching pressures

1. Compressor off (switch opens) 1.45 up to 1.6 bar pressure
2. Compressor on (switch closes) 2.9 to 3.4 bar pressure

1. Unplug connector -A-.
2. Replace O-ring -B- (8.9 x 1.8 mm). Tightening torque: 5 Nm (44 in. lb)

Note. To test the A/C system cooling performance, with the switch removed, bridge the two terminals in connector -A-. The refrigerant system remains closed due to the Schrader valve.

A/C pressure switch -F129-, functions

The high/low pressure switch (located between terminals -1- and -2-) switches the compressor off (via A/C control head - E87-) when there is an excessively high or low pressure in the A/C system.

Scheme 18

Switching pressures (in bar)

Switch open (compressor off)

1. Low pressure: switch opens at 1.2 bar (17.4 psi) and closes at 1.8 bar (25.2 psi)
2. High pressure: switch opens at 30 bar (420 psi) and closes at 14.5 bar (203 psi)

Switch closed (compressor on)

1. 1.2 (1.8) bar to 30 (14.5) bar

The high pressure switch (between terminals -3- and -4-) switches coolant fan -V7- to speed 2.

Switching pressures (in bar)

1. Fan speed 2 on (switch closes) at 16 bar (232 psi)
2. Fan speed 2 off (switch opens) at 12.5 bar (181 psi)

Scheme 19

1. Remove bumper See «BUMPER»(/audi/a8/d2-1994-1999/remont/exterior-body-panels/#bumper) .
2. Disconnect harness connector.
3. Remove A/C pressure switch -B-. Tightening torque: 5 Nm (44 in. lb)
4. Replace O-ring seal -A- (10.8 mm x 1.8 mm). See «O-rings»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__o-rings) .
5. To test cooling efficiency with switch removed, bridge terminals -1- and -2- on harness connector -B-. The A/C refrigerant circuit remains closed due to the Schrader valve in the line connection.

Testing

1. Start engine. Compressor switched on (AUTO mode selected)

If the compressor is activated

1. Disconnect harness connector -B- from switch. Compressor will stop (low pressure switch open).
2. Remove switch -A- and install harness connector -B-. Compressor will not be activated (low pressure switch open).

If the compressor is not activated

1. Disconnect harness connector -B- from switch -A- and bridge terminals -1- and -2- on harness connector -B-. The compressor will be activated.

Note. If the compressor is activated when the terminals are connected together, either the pressure in the A/C system is too low (A/C system empty), or the switch is malfunctioning. Check the pressure in the refrigerant circuit. See A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES . If the compressor is not activated and the measuring value block display indicates A/C pressure switch -F129- as the cut-off condition, find and repair the open circuit in the wiring between A/C pressure switch -F129- and A/C control head -E87-.

O-rings for refrigerant system

1. Always use O-rings only once, always replace.
2. Moisten with refrigerant (PAG) oil before installing.
3. Make sure seal is correctly located on the line or in the groove.
4. Handle O-rings only in a clean working environment.

Note. Only O-rings which are resistant to R-134a refrigerant and to the relevant refrigerant oil may be installed (only original parts make sure of this). Such O-rings are colored in order to eliminate any confusion (at present "red" or "violet").

Scheme 20

A/C compressor from mounting bracket, removing and installing

1. Remove noise insulation. See «NOISE INSULATION PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/exterior-body-panels/#body-front__noise-insulation-panel-removing-and-installing) .

1. Remove ribbed V-belt. See «RIBBED BELT, REMOVING AND INSTALLING»(ref-196865-S24437602202005100900000) .
2. Remove bolts -A- and -B-. Tightening torque: 25 Nm (18 ft lb)

Note. Removing and installing the mounting bracket for compressor and power steering pump.

See MOUNTING BRACKET .

1. When installing the compressor, make sure that the two centering sleeves -C- are correctly located.
2. When installing, make sure that wiring to A/C clutch -N25- is correctly routed.
3. Before installing the ribbed V-belt, check that the belt pulleys are properly aligned. See «RIBBED BELT, REMOVING AND INSTALLING»(ref-196865-S24437602202005100900000) .

Nippondenso compressor

Note. Remove ribbed V-belt. See RIBBED BELT, REMOVING AND INSTALLING . Before removing ribbed V-belt, mark its running direction.

Note. The following list refers to items in (Scheme 26).

1. Bolt 15 Nm (11 ft lb) Removing, installing. See «REMOVING AND INSTALLING CLUTCH PLATE BOLT»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__removing-and-installing-clutch-plate-bolt) .
2. Clutch disc Pulling off. See «PULLING OFF CLUTCH DISC»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__pulling-off-clutch-disc) .
3. Shims For adjusting the gap between clutch disc and belt pulley Size of gap: 0.3 to 0.6 mm Checking and adjusting gap. See «CHECKING AND ADJUSTING GAP»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__checking-and-adjusting-gap) .
4. Circlip Always replace Install with flat side facing compressor Make sure circlip is correctly located in the groove
5. Belt pulley Remove with commercial two or three arm puller Use care to make sure belt pulley is not damaged
6. Circlip Always replace Install with flat side facing compressor Make sure circlip is correctly located in the groove
7. Magnetic coil Installing. See «INSTALLING MAGNETIC COIL»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__installing-magnetic-coil) . With overheat fuse installed (interrupts circuit when coil overheats, in case of excessive compressor load e.g. hard to turn) With current protection diode -J201- (reduces voltage peaks which may occur when A/C clutch is shut off)
8. Bolt
9. A/C compressor (Nippondenso)

Scheme 21

Removing and installing clutch plate bolt

Tightening torque: 15 Nm (11 ft lb)

Note. Use commercially available strap wrench -A-with fabric band to counterhold clutch disc.

Scheme 22

Pulling off clutch disc

1. Pry off carefully with screwdrivers.

Scheme 23

Note. With a tight fitting clutch disc, use commercial two or three-arm puller.

Installing magnetic coil

1. Align tab -A- in recess -B-.

Scheme 24

Checking and adjusting gap

1. Measure gap between belt pulley and clutch plate using depth gauge -C- at 3 points. This is measurement -1-.
2. Apply 12V DC to magnetic coil. Positive B+ voltage to single pin connector -A- Ground (-) to A/C compressor housing -B
3. Measure gap again between pulley and clutch disc measured with gauge -C-. This is measurement -2-. Difference between two measurements -1- and -2- must be: 0.4 to 0.6 mm (0.016 to 0.024 in.)

Note. The gap must lie within tolerances around the entire circumference. Gap can also be measured with compressor installed. If gap dimension lies outside of the permissible range, remove clutch disc and adjust gap dimension by removing or inserting spacer.

Automatic Climate Control components in engine compartment, servicing

1. After performing repairs, always check and erase DTC memory, perform basic setting and also check coding of A/C control head -E87-. See «VAG 1551 (VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
2. A/C system cooling performance. See «A/C REFRIGERANT SYSTEM, TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
3. A/C system servicing. See «A/C SYSTEM REFRIGERANT SYSTEM, SERVICING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-system-refrigerant-system-servicing) .
4. All the components identified with an asterisk (*) are actuated during output Diagnostic Test Mode (DTM). See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__output-diagnostic-test-mode-dtm-function) .
5. Different codes on the A/C control head -E87- for Nippondenso compressor without speed sensor -G111-. See «CODE CONTROL MODULE (FUNCTION 07)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__code-control-module-function-07) .
6. An electrical test is possible at all the components identified with two asterisks (**). See «AUTOMATIC CLIMATE CONTROL SYSTEM, ELECTRICAL»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .

Note. The following list refers to items in (Scheme 31) and (Scheme 32).

1. Outside air temperature sensor -G17-** Removing and installing: to remove bumper, unplug connector and unclip sensor from mount in the air guide
2. A/C refrigerant pressure switches -F23-, -F118- and -F129-** A/C pressure switch - F129-, function, removing and installing. See «A/C PRESSURE SWITCH -F129-, FUNCTIONS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-pressure-switch-f129-functions) . A/C high pressure switch -F23- and -F118- function, removing and installing. See «A/C refrigerant high pressure switches -F23- and -F118»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . NOTE: A/C refrigerant high pressure switch -F23- and A/C refrigerant high pressure switch -F118- are installed on vehicles with an A/C control headup to Part No. index letter "H." On vehicles with an A/C control head beginning at Part No. index letter "J," A/C pressure switch -F129- is installed (introduction of sensor for air quality -G238-).
3. A/C clutch -N25-* Servicing. See «A/C CLUTCH, SERVICING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
4. A/C compressor speed sensor -G111-** Not applicable for Nippondenso compressor
5. Compressor (Nippondenso) Removing and installing compressor from mounting bracket. See «A/C COMPRESSOR FROM MOUNTING BRACKET, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-compressor-from-mounting-bracket-removing) . Removing and installing. See «A/C COMPRESSOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-compressor-removing-and-installing) . CAUTION: Discharge A/C refrigerant system before removing A/C compressor. NOTE: Remove ribbed V-belt. See «RIBBED BELT, REMOVING AND INSTALLING»(ref-196865-S24437602202005100900000) .
6. Accumulator Removing and installing. See «ACCUMULATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . CAUTION: Discharge A/C refrigerant system before removing accumulator.
7. A/C refrigerant low pressure switch -F73-** Function, removing and installing. See «A/C REFRIGERANT LOW PRESSURE SWITCH -F73»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . Deleted with introduction of A/C pressure switch - F129-. See «A/C pressure switch -F129-, functions»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-pressure-switch-f129-functions) . For vehicles without A/C refrigerant low pressure switch -F73- a cap with seal must be screwed onto the connector for this switch
8. Forced air ventilation The sealing lips of the ventilation frame must be free of obstructions and must close automatically. NOTE: To ensure proper ventilation of the passenger compartment, the position of the air guides formed by luggage compartment trim (to the parcel shelf) must not be altered.
9. Dust and pollen filter Removing and installing. See «DUST AND POLLEN FILTERS, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__dust-and-pollen-filters-removing-and) . Observe notes regarding revised version for vehicles with sensor for air quality -G238-. See «DUST AND POLLEN FILTERS, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__dust-and-pollen-filters-removing-and) . NOTE: The dust and pollen filters must be replaced at regular intervals.
10. Pump valve unit Removing and installing. See «PUMP VALVE UNIT, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__pump-valve-unit-removing-and-installing) . Replacing. See «PUMP VALVE UNIT, REPLACING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__pump-valve-unit-replacing) . NOTE: The pump valve unit consists of the left and right heat regulating valves -N175- and -N176- as well as coolant pump -V50-.
11. Fresh air intake duct temperature sensor -G89-** Removing and installing. See «FRESH AIR INTAKE DUCT TEMPERATURE SENSOR -G89-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
12. Air flow flap motor -V71-* With back pressure flap motor position sensor - G113- Removing and installing. See «AIR FLOW FLAP MOTOR -V71-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__air-flow-flap-motor-v71-removing) .
13. Evaporator Removing and installing. See «A/C EVAPORATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-evaporator-removing-and-installing) . CAUTION: Discharge A/C Refrigerant System Before Removing Evaporator.
14. Opening for recirculating air mode
15. Recirculation flap motor -V113-* With recirculation flap motor position sensor - G143- Removing and installing. See «RECIRCULATION FLAP MOTOR -V113-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__recirculation-flap-motor-v113-removing-and) .
16. Fresh air blower - V2-** Removing and installing. See «FRESH AIR BLOWER -V2-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning)
17. Control unit for blower - J126-** Removing and installing. See «CONTROL MODULE FOR FRESH AIR BLOWER -J126-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__control-module-for-fresh-air-blower) .
18. Condenser Removing and installing. See «A/C CONDENSER, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-condenser-removing-and-installing) . CAUTION: Discharge A/C refrigerant system before removing condenser.
19. Service valve For measuring, draining and filling NOTE: A cap with seal must be installed.
20. Sensor for air quality - G238- Phased into production in m.y. 1998 For vehicles with sensor for air quality -G238- only one compatible version of A/C control head -E87- is or should be installed beginning at Part No. index letter "J" Function: See «Sensor for air quality -G238-, function»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__sensor-for-air-quality-g238-function) . Checking: See «SENSOR FOR AIR QUALITY -G238-, CHECKING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . Removing and installing. See «SENSOR FOR AIR QUALITY -G238-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__sensor-for-air-quality-g238-removing) .
21. Fresh air intake duct temperature sensor -G89-** Removing and installing. See «FRESH AIR INTAKE DUCT TEMPERATURE SENSOR -G89-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . Component location for vehicles equipped with sensor for air quality - G238

Scheme 25

Scheme 26

Sensor for air quality -G238-, function

The sensor for air quality -G238- recognizes pollutants in the recirculating air (mostly gasoline and/or diesel exhaust) and relies on A/C control head -E87- to switch to the recirculating air mode.

The A/C control head receives a signal from the sensor for air quality -G238- from which the type and amount of air pollution is determined. Depending on the outside temperature and the amount of air pollution, the A/C control head then decides

1. At an outside temperature greater than approx. +2°C (36°F) the recirculating air mode is switched on when there is only a slight increase in pollutants.
2. At an outside temperature of approx. +2°C (36°F) and - 8°C (-18°F) only after a stronger increase of pollutant concentration is there a changeover to the recirculating air mode (compressor simultaneously switches on).
3. At an outside temperature less than -8°C (-18°F) a changeover occurs after a severe increase of pollutant concentration, and only for 15 seconds (the compressor is not shut off). If the concentration drops, the A/C switches over to the fresh air mode.

The function "Automatic air recirculation" can be switched off at any time. If the function is active, the compressor switches on when "Automatic air recirculation" is requested and also with an outside temperature less than +2°C (36°F). At a temperature of less than -8°C (-18°F), compressor operation is no longer possible.

To ensure that the A/C does not operate constantly in the recirculating air mode in areas with a consistently higher pollution, the sensor is self-learning (it adjusts its sensitivity to the environmental conditions).

If the pollutant load of the outside air remains relatively high over a longer period of time, the sensor starts a learn program to assimilate to the changed environmental conditions, so that a recirculating air requirement occurs within less than 12 minutes. If numerous load peaks occur in sequence, the A/C can work for a longer time in recirculating air mode.

Note. A specific amount of time is needed for the A/C flaps to change-over. In the event that a sudden increase in pollutants is encountered (e.g. when driving through a diesel exhaust cloud) gas forming pollutants can be taken in with the fresh air into the passenger compartment until the flap can be closed. For this reason, a dust and pollen filter is installed with the charcoal layer. A filter that has become saturated with pollutants is no longer effective and needs to be replaced. See Dust and pollen filters, removing and installing . In order to avoid quick shifting from the recirculating/fresh air flap, a slight increase in pollutants entering with recirculating air will not allow for immediate shifting (the sensor does not send a signal to the sensor for air quality - E87-). The filtering of the charcoal insert in the dust and pollen filter will be sufficient. See DUST AND POLLEN FILTERS, REMOVING AND INSTALLING . In order to avoid quick shifting from the recirculating air/fresh air flap, the requirement from the sensor for "Automatic air recirculation" mode is at least 35 seconds (minimum duration period), especially if the pollutant concentration has been reduced considerably so that recirculating air mode is no longer necessary. If the compressor is shut off (e.g. in "ECON" operating mode) so that the windows do not fog up, the maximum duration of the "Automatic air recirculation" mode from A/C control head -E87- is limited to approx. 15 seconds. In order to defrost windows as quick as possible, recirculating air mode is not possible with A/C control head -E87- in the "defrost" operating mode. Sensor for air quality -G238- requires approx. 30 seconds to be operational after switching the ignition on (warm-up time). During this time there is no requirement from the sensor to A/C control head -E87- for "Automatic air recirculation" mode. Sensor for air quality -G238- contains a highly sensitive electronic component which can be damaged if it comes in direct contact with solvents, fuels or chemicals. Therefore, do not install sensors which have come in contact with such substances.

Test requirements

1. Vehicle is in an area where there is clean recirculating air (not near running engines, openings from exhaust systems, etc.)
2. Engine compartment and plenum chamber are clean (not contaminated with oil and/or fuel)
3. The engine compartment and plenum chamber were not sprayed with cleaning or preservative solutions

Preparation

1. Check DTC memory.

Scheme 27

If a DTC is recognized, repair and eliminate all malfunctions. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02) .

1. Remove plenum chamber cover.

Scheme 28

1. Switch ignition on.
2. Set A/C control head -E87- to "Auto" operating mode.
3. Start engine (compressor on).
4. Press button for "Automatic air recirculation" (lamp in -A- button comes on).
5. Wait 30 seconds (warm-up time of sensor for air quality -G238-).
6. Connect VAG 1551 Scan Tool (ST) to 16-pin Data Link Connector (DLC) using VAG 1551/3 adapter cable. See «VAG 1551 (VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
7. Start engine. The on board diagnostic function for A/C control head -E87- begins (address word "08"). See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) . Indicated on display
8. Press buttons -0- and -8- to select "Read Measuring Value Block" function 08. Indicated on display
9. Press -Q- button to confirm input. Indicated on display
10. Input display group number "01" (overview. See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) ).
11. Press -Q- button to confirm input. Indicated on display

Scheme 29

1. Display "0" in display field 1 shows the compressor switched on (there is no compressor cut-off condition).
2. Table of possible displays in display field 1. See «DISPLAY GROUP 001 - A/C COMPRESSOR CUT-OFF CONDITIONS, VOLTAGE FOR A/C CLUTCH -N25-, VOLTAGE TO TERMINAL 15 AND REQUIREMENT FOR RECIRCULATING AIR MODE/SENSOR FOR AIR QUALITY -G238»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__display-group-001-ac-compressor) .
3. The voltage for the A/C clutch -N25- is displayed in display field 2 (for example, 12.5 V).
4. Display field 3 shows the voltage to terminal 15 (for example, 12.5 V).
5. Display field 4 shows operating condition of the fresh/recirculating air. Table of possible displays in display field 4. See «DISPLAY GROUP 001 - A/C COMPRESSOR CUT-OFF CONDITIONS, VOLTAGE FOR A/C CLUTCH -N25-, VOLTAGE TO TERMINAL 15 AND REQUIREMENT FOR RECIRCULATING AIR MODE/SENSOR FOR AIR QUALITY -G238»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__display-group-001-ac-compressor) .

Scheme 30

Scheme 31

1. Read display from display field 4.
2. Specified values: "00" (no requirement for "recirculating air", A/C in fresh air mode with fresh air operation) or "60" ("Partial recirculating air," fresh air and recirculating air flap open)
3. Place spray head -A- of test bottle over air inlet of sensor for air quality -B-.
4. Activate spray head -C- of test bottle for 1 second.

Note. The content of the test gas bottle consists of pure oxygen with a specified amount of nitrogen oxide. The test gas for the air quality sensor is obtained as a replacement part under the number D007 855 A2. If the sensor comes in contact with cigarette smoke or gas from a lighter it will react.

1. Read display from display field 4. Specified value: "10" (requirement for "Automatic air recirculation" available, requirement is fulfilled, A/C switches to recirculating air mode)
2. Wait a short period of time (approx. 1 minute, depending on amount of test gas sprayed in sensor).
3. Read display field 4. Specified value: "00" (no requirement for "Recirculating air," A/C system in fresh air mode or "60" (partial recirculating air)

Note. In order to avoid quick shifting from the recirculating air/fresh air flap, the requirement from the sensor for "Automatic air recirculation mode" is at least 25 seconds (minimum duration period) especially if the pollutant concentration has been reduced considerably so that recirculating air mode is no longer necessary.

Scheme 32

Scheme 33

1. Operate switch for wiper/washer system until windshield washer pump -V5- has been cycled for approx. 2 seconds.
2. Read display from display field. Specified value: "30" (requirement for recirculating air due to washer/wiper system, A/C switches for approx. 10 seconds to the recirculating air mode)
3. Wait a short period of time.
4. Read display from display field 4. Specified Values: "00" (no requirement for "recirculating air, A/C in fresh air mode) or "60" (partial recirculating mode)

Note. Depending on the composition of the windshield washer fluid, the sensor can determine impurities in the air and request for "Automatic air recirculation." If when activating the wiper/washer system the mode does not switch over to recirculating air, check the wiring connection between A/C control head -E87- and wiper/washer intermittent relay -J31- according to the wiring diagram.

Scheme 34

1. Press --> button. Indicated on display
2. Push buttons -0- and -6- to select "End Output" function 06. Indicated on display
3. Press -Q- button to confirm input. Indicated on display
4. Switch ignition off and disconnect Data Link Connector (DLC).

Note. If the function of the sensor for air quality -G238- is OK for this test and there is a customer complaint continue as follows

1. Check dust and pollen filter for dirt.
2. Close DTC unit and select "Read Measuring Value Block" function 08.
3. Drive vehicle to area with relatively clean recirculating air (the system works in fresh air mode).
4. Now drive vehicle into an area with heavily polluted recirculating air (for example, on a street with construction or and truck traffic).

Display field 4, display group 001 must change from 00 or 60 to 10 when driving through a diesel exhaust cloud.

1. Read the notes. See «SENSOR FOR AIR QUALITY -G238-, FUNCTION»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__sensor-for-air-quality-g238-function) .

Sensor for air quality -G238-, removing and installing

Note. Sensor for air quality -G238- contains a highly sensitive electronic component which can be damaged if it comes in direct contact with solvents, fuels or chemicals. Therefore, do not install sensors which have come in contact with such substances. Do not install a sensor that was stored in a tool box. A removed sensor should not be placed in an area where it can come in contact with solutions, fuel and/or specific chemicals (fluid or dampness).

Scheme 35

1. Remove plenum chamber cover.
2. Remove harness connector -A- from sensor. (Scheme 50)
3. Remove screw -B- and sensor.

Terminals in connector -A- are as follows

Scheme 36

1. Terminal 1: Plus (terminal "15")
2. Terminal 2: Minus (terminal "31")
3. Terminal 3: Signal wire to A/C control head -E87- (square wave signal not measurable)
4. Terminal 4: Not occupied

Air flow flap motor -V71-, removing and installing

Note. Mark connecting element motor/flap when removing (danger of swapping with connecting elements of the other actuator motors). For the malfunction "adaptation limit exceeded", check connecting element at motor, there must be no play between the shaft of the actuator motor and the connecting element. If the actuator motor makes clicking or rattling noises in regular intervals (approx. every 7 minutes), observe notes on FLAP AND VENT MOTORS, SERVICING (actuator motors for center vent, removing and installing).

1. Remove plenum cover.
2. Remove cover with air flow flap.
3. Remove 2 screws -A- and remove flap motor.

Scheme 37

Note. Before installing the motor, check mounting of the air flow flap (knob -C- must be positioned between the stops -D-). If shaft of motor is positioned in such a way that it is not possible to install motor, see instructions regarding installation. See LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING . Tighten securing screws -A- only by hand, tightening torque 8 Ncm (0.7 in. lb). After installing cover, check that grommet -B- is correctly located. After installing, always check DTC memory. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02) .

Scheme 38

1. Remove plenum cover.
2. Rotate temperature sensor -A- approx. 90° (1/4 turn) and remove.

Scheme 39

1. Remove plenum cover.
2. Remove cover grille (for air flow flap).
3. Switch ignition off.
4. Remove air flow flap motor -V71-. See «AIR FLOW FLAP MOTOR -V71-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__air-flow-flap-motor-v71-removing).
5. Remove 3 screws each -A- and -B-. (Scheme 54)
6. Pry off clips -C-.
7. Remove cover with air flow flap.

Scheme 40

Scheme 41

1. Remove plenum cover.
2. Remove windshield wipers and cowl panel complete. See «WIPER/WASHER SYSTEMS»(/audi/a8/d2-1994-1999/remont/wiperwasher-systems/#wiperwasher-systems) (1997-99), or «WINDSHIELD WIPER SYSTEM, SERVICING»(ref-196903-S19054507702005101000000) (2000-2003).
3. Remove cover with air flow flap. See «COVER WITH AIR FLOW FLAP, REMOVING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
4. Remove 4 screws -A-, pry off clips -B- and remove cover together with recirculating air flap from the air conditioner assembly.
5. Remove both air guide rings -A-. (Scheme 56)
6. Remove 2 screws -B- and 2 screws -C-.
7. Remove air guide -D-.
8. Remove 2 screws -A- and remove hoop -B-.
9. Remove fresh air blower.

Note. When installing, make sure that connection -C- is correctly routed.

Scheme 42

Recirculation flap motor -V113-, removing and installing

Note. Mark connecting element motor/flap when removing (danger of swapping with connecting elements of the other actuator motors). For the malfunction "adaptation limit exceeded" check connecting element at motor, there must be no play between the shaft of the actuator motor and the connecting element. If the actuator motor makes clicking or rattling noises in regular intervals (approx. every 7 minutes), observe notes on FLAP AND VENT MOTORS, SERVICING (actuator motors for center vent, removing and installing).

Scheme 43

Scheme 44

1. Remove plenum cover.
2. Remove windshield wipers and cowl panel complete See «WIPER/WASHER SYSTEMS»(/audi/a8/d2-1994-1999/remont/wiperwasher-systems/#wiperwasher-systems) (1997-99), or «WINDSHIELD WIPER SYSTEM, SERVICING»(ref-196903-S19054507702005101000000) (2000-2003).
3. Remove cover with air flow flap. See «COVER WITH AIR FLOW FLAP, REMOVING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
4. Remove 4 screws -A-, pry off clips -B- and remove cover together with recirculating air flap from the air conditioner assembly.
5. Remove cover.
6. Remove 2 screws -A- and remove flap motor.

1. Before installing flap motor, check mounting of the air flow flap (knob -C- must be positioned between the stops -D-).
2. If the shaft of the motor is positioned in such a way that it is not possible to install the motor, see instructions regarding installation. See «LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-center-vent-motor-v110-and) .
3. Tighten securing screws -A- only by hand, tightening torque 8 Ncm (0.7 in. lb).
4. After installing the cover, check that the grommet -B- is correctly located.
5. After installing, always check DTC memory. See «DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__diagnostic-trouble-code-dtc-memory-checking) .

Control module for fresh air blower -J126-, removing and installing

1. Remove plenum cover.
2. Remove cover with air flow flap. See «COVER WITH AIR FLOW FLAP, REMOVING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning). WARNING: Heat sink -C- may be hot.
3. Remove 2 screws -A-. (Scheme 60)

Scheme 45

Note. Route harness connection -B- to control module -J126- (Scheme 60) The heat sink of control module -J126- may be hot. Remove the foam seal -C- from the control module supplied as a replacement part before installing.

Pump valve unit, removing and installing

Note. As of January 2001, the production will be switched gradually to a revised pump-valve unit (a different coolant pump -V50-). For this version, the vehicle wiring harness is connected directly to the pump. If the pump-valve unit must be replaced on a vehicle built with the conversion, a wire adapter must also be used in case the changed version is installed. Mark the allocation of the coolant hoses -A- (supply to pump-valve unit) and -B- (return to engine). (Scheme 61)

Scheme 46

1. Switch ignition off.
2. Remove vacuum brake booster. See «POWER BRAKE BOOSTER»(/audi/a8/d2-1994-1999/remont/mechanical-hydraulic/#disc-brakes) .

Note. If the coolant pump -V50- produces noises, check that the cooling system is completely bled before removing the pump valve unit (air in cooling system can produce noises). See COOLING SYSTEM, DRAINING AND FILLING (1997-99), or COOLING SYSTEM, DRAINING AND FILLING (2000-2003).

Scheme 47

Scheme 48

Scheme 49

1. Release pressure in the cooling system by opening the cap on the coolant expansion tank and drain cooling system into a clean container.
2. Disconnect both coolant hoses from engine to pump valve unit (-A- and -B-) and mark arrangement of coolant hoses.
3. Remove cover with air flow flap. See «COVER WITH AIR FLOW FLAP, REMOVING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
4. Hold coolant hose -A- in clean container.
5. Carefully blow coolant out of the pump valve unit and heater cores through coolant hose -B- with compressed air.
6. Remove reinforcing plate (plenum). See «REINFORCING PLATE (PLENUM), REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
7. Mark coolant hoses -A- and -B- and disconnect from coolant hoses running to the heater cores.
8. Remove securing bolts -C-. (Scheme 63)
9. Disconnect pump valve unit from the rubber mounts -B-. (Scheme 64)
10. Pull pump valve unit far enough to the right until the two clips at coolant hoses -A- (at the pump valve unit) are accessible.
11. Mark coolant hoses -A- and disconnect from the pump valve unit.
12. Remove pump valve unit together with coolant hoses.

1. Tightening torques of bolts -A-: 10 Nm (7 ft lb).
2. Connect coolant hoses to the heater core correctly (bottom hose = coolant supply, top hose = coolant return).
3. The coolant pump -V50- of the pump valve unit must not be operated until the cooling system has been bled (dry running will damage the pump). For this reason, do not connect the 2-pin connector to pump valve unit until after bleeding the cooling system.
4. Connect coolant hoses to the engine correctly (pay attention to markings made).
5. Bleed cooling system See «COOLING SYSTEM, DRAINING AND FILLING»(ref-196862-S32357803552005100900000) (1997-99), or «COOLING SYSTEM, DRAINING AND FILLING»(ref-196866-S33984552662005100900000) (2000-2003).
6. Check that grommet between engine compartment and plenum is correctly located after installing.

Pump valve unit, replacing

1. Remove pump valve unit. See «PUMP VALVE UNIT, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__pump-valve-unit-removing-and-installing).
2. Remove screws -A-. (Scheme 65)
3. Remove bracket -B-.
4. Remove coolant hoses (hoses -C- to heater core on passenger side, hoses -D- to heater core on passenger side, hoses -D- to heather core on driver side).

Scheme 50

Note. Replace O-rings -E-. Insert rubber mounts -F- in the pump valve unit and in the bracket -G- as shown in the figure.

Dust and pollen filters, removing and installing

1. Press in quick-lock -A- slightly and turn approx. 90° (1/4 turn). (Scheme 66)

Note. The two dust and pollen filters must be replaced at certain intervals and always both filters at the same time.

See maintenance schedule.

Scheme 51

1. With the introduction of the sensor for air quality -G238- a revised dust and pollen filter is installed. This filter consists of an additional filter insert with active charcoal. See «SENSOR FOR AIR QUALITY -G238-, FUNCTION»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__sensor-for-air-quality-g238-function) .
2. The filter with its activated charcoal insert functions as a dust and pollen filter, but can also filter out gas forming pollutants such as ozone, benzol, nitrogen dioxide etc. from the air flow.
3. The activated charcoal filter collects gas forming pollutants which flow through the air until the fresh air flap has closed and the A/C function switches to the recirculating air mode. The change-over from fresh to circulating air mode occurs as soon as the sensor for air quality -G238- recognizes gas forming pollutants in the surrounding air via A/C control head -E87- (the function "Automatic air recirculation" must be selected).
4. The activated charcoal layer in the dust and pollen filter affects the pollutants in the air differently. Specific pollutants are bound securely to the activated charcoal layer, while others are changed in a catalyst into non-damaging particles. For the remainder the activated charcoal works like a condenser. When the load increases, the pollutants are taken up only to a specific saturation point, removing that percentage of pollutants, continuously handing off those particles to the activated charcoal layer.

Since the activated charcoal layer binds one part of the pollutant particles, it is important to change the dust and pollen filter earlier than specified

1. When operating the vehicle in areas of heavy air pollution.
2. When operating the vehicle with "Automatic air recirculation" shut off.
3. For vehicles without the sensor for air quality -G238- and without the "Automatic air recirculation" function.

For vehicles with the air quality sensor the A/C should, if possible, always be in the "Automatic air recirculation" mode. If it is necessary or requested to shut off the function, the following must be noted

1. The activated charcoal layer in the dust and pollen filter can become saturated over time.
2. A saturated filter cannot collect anymore particles and will hinder the flow process.

The essential function of the dust and pollen filter and the sensor for air quality is that it removes peak pollutants from the passenger compartment. Therefore, the following must be noted

1. It is recommended to change-over from fresh to Automatic air recirculation mode while the vehicle is being driven through an area with relatively clean recirculating air (low concentration of pollutants in the air) rather than when in an area with a higher concentration of pollutants (e.g. industrial areas).
2. The changeover from fresh to recirculating air occurs independent of the base level of pollutants, but always occurs when the concentration of pollution increases (e.g. when driving through an exhaust cloud of a diesel truck).

The charcoal filter can be installed on all vehicles (including vehicles without the sensor for air quality). However, for these vehicles the same limitations apply as when operating the A/C with the "Automatic air recirculation" function switched off.

Scheme 52

1. Remove intake hose (from air filter to engine).
2. Disconnect soundproofing mat from front wall of plenum.
3. Remove bolts -A- and nuts -B-.
4. Remove reinforcing plate.

Automatic Climate Control components in passenger compartment, servicing

1. After performing repairs, always check and erase the DTC memory, perform basic setting and check coding of A/C control head -E87-.
2. A/C system cooling performance: See «A/C REFRIGERANT SYSTEM, TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
3. A/C system servicing: See «A/C SYSTEM REFRIGERANT SYSTEM, SERVICING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-system-refrigerant-system-servicing) .
4. All components identified with an asterisk (*) are actuated during output Diagnostic Test Mode (DTM). See «OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__output-diagnostic-test-mode-dtm-function) .
5. An electrical test is possible at all the components identified with two asterisks (**). See «AUTOMATIC CLIMATE CONTROL SYSTEM, ELECTRICAL»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
6. The air outlets to the windshield (defrost) can only be replaced if the instrument panel is removed. Separate instrument panel and instrument panel cross member.
7. Changes to model year 2000 vehicles: See «CLIMATE CONTROL COMPONENTS IN PASSENGER COMPARTMENT, UPDATES FROM M.Y. 2000»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__climate-control-components-in-passenger-compartment) .

Note. The following list refers to items in (Scheme 68).

1. Kick-down switch Depending on vehicle equipment and momentary vehicle speed, A/C clutch is switched off on acceleration by either Engine Control Module (ECM) or Transmission Control Module (TCM). See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) .
2. A/C control head -E87- Allocation. See «A/C CONTROL HEAD -E87-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-control-head-e87-removing-and) . Removing and installing. See «A/C CONTROL HEAD -E87-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-control-head-e87-removing-and) . Replacing bulbs of A/C control head panel. See «A/C CONTROL HEAD -E87-, REPLACING BULBS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . NOTE: Vehicles with Nippondenso compressor may only have A/C control heads beginning with Index "C" installed. See «VAG 1551 ((VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) . Depending on the equipment level of the vehicle, different versions of A/C control head -E87- are installed (with and without sensor for air quality, etc.). See «A/C CONTROL HEAD -E87-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-control-head-e87-removing-and) .
3. Instrument panel interior temperature sensor -G56-** Removing and installing. See «INSTRUMENT PANEL INTERIOR TEMPERATURE SENSOR -G56-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__instrument-panel-interior-temperature-sensor-g56) .
4. Data Link Connector (DLC) Connecting VAG 1551 and testing A/C system. See «VAG 1551 ((VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
5. Lower air outlet in right (left) of instrument panel Removing and installing. See «LOWER AIR OUTLET IN RIGHT (LEFT) OF INSTRUMENT PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
6. Upper air outlet in right (left) of instrument panel Removing and installing. See «UPPER AIR OUTLET IN RIGHT (LEFT) OF INSTRUMENT PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
7. Side window air outlet in right (left) of instrument panel Removing and installing. See «SIDE WINDOW AIR OUTLET IN RIGHT (LEFT) OF INSTRUMENT PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__side-window-air-outlet-in-right) .
8. Right center vent switch -F184-** Removing and installing air outlet. See «CENTER AIR OUTLET IN INSTRUMENT PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__center-air-outlet-in-instrument-panel) .
9. Center vent position sensor -G142-** Removing and installing air outlet. See «CENTER AIR OUTLET IN INSTRUMENT PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__center-air-outlet-in-instrument-panel) .
10. Sunlight photo sensor - G107-** Removing and installing. See «SUNLIGHT PHOTO SENSOR -G107-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
11. Left center vent switch - F183-** Removing and installing air outlet. See «CENTER AIR OUTLET IN INSTRUMENT PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__center-air-outlet-in-instrument-panel) .
12. Auto check system with outside air temperature display -G106-* Outside air temperature supplied by -E87- is only displayed when a Drive mode is engaged. For vehicles with A/C control head -E87- with part number as of index "M", the displayed temperature is calculated directly in the instrument cluster and displayed there with the selected unit of °C or °F. NOTE: If readout is faulty, test measured values of temperature sensors. See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) .
13. Condensation drain hose (with valve) on passenger side Checking, removing and installing. See «CONDENSATION DRAIN HOSE WITH VALVE (DRIVER/PASSENGER SIDE), CHECKING, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
14. Right footwell flap motor -V109-* With right footwell flap motor position sensor - G140- Removing and installing. See «TEMPERATURE REGULATOR FLAP MOTOR -V68- AND RIGHT FOOTWELL FLAP MOTOR -V109-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__temperature-regulator-flap-motor-v68-and) .
15. Right vent temperature sensor -G151-** Removing and installing. See «LEFT VENT TEMPERATURE SENSOR -G150- AND RIGHT VENT TEMPERATURE SENSOR -G151-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
16. Temperature regulator flap motor -V68-* With temperature regulator flap motor position sensor -G92- Removing and installing. See «TEMPERATURE REGULATOR FLAP MOTOR -V68- AND RIGHT FOOTWELL FLAP MOTOR -V109-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__temperature-regulator-flap-motor-v68-and) .
17. Heater core, passenger side Removing and installing. See «PASSENGER-SIDE HEATER CORE, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__passenger-side-heater-core-removing-and-installing) .
18. Right center vent motor - V111-* With right center vent motor position sensor - G137- Removing and installing. See «LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-center-vent-motor-v110-and) .
19. Left vent temperature sensor -G150-** Removing and installing. See «LEFT VENT TEMPERATURE SENSOR -G150- AND RIGHT VENT TEMPERATURE SENSOR -G151-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
20. Defroster flap motor - V107-* With defroster flap motor position sensor -G135- Removing and installing. See «DEFROSTER FLAP MOTOR -V107-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__defroster-flap-motor-v107-removing-and) .
21. Left center vent motor - V110-* With left center vent motor position sensor - G136- Removing and installing. See «LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-center-vent-motor-v110-and) .
22. Interior temperature sensor fan -V42- Removing and installing. See «INTERIOR TEMPERATURE SENSOR FAN -V42-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
23. Rear footwell vent motor -V112-* With rear footwell vent motor position sensor - G141- Removing and installing. See «LEFT FOOTWELL FLAP MOTOR -V108- AND REAR FOOTWELL VENT MOTOR -V112-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-footwell-flap-motor-v108-and) .
24. Center vent adjusting motor -V102-* With center vent motor position sensor -G138- Removing and installing. See «CENTER VENT ADJUSTING MOTOR -V102-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__center-vent-adjusting-motor-v102-removing) .
25. Left footwell flap motor - V108-* With left footwell flap motor position sensor - G139- Removing and installing. See «LEFT FOOTWELL FLAP MOTOR -V108- AND REAR FOOTWELL VENT MOTOR -V112-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-footwell-flap-motor-v108-and) .
26. Heater core, driver side Removing and installing. See «DRIVER-SIDE HEATER CORE, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__driver-side-heater-core-removing-and-installing) .
27. Condensation drain hose (with valve) on driver side Checking, removing and installing. See «CONDENSATION DRAIN HOSE WITH VALVE (DRIVER/PASSENGER SIDE), CHECKING, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .

Scheme 53

A/C control head -E87-, removing and installing

Note. Always check DTC memory before removing -E87-. Changes to model year 2000 vehicles. See Changes to model year 2000 vehicles After replacing -E87-, always: Check coding or enter new coding. Perform basic setting. Re-check DTC memory. If a newly installed A/C control head -E87- flashes after ignition is switched on, code -E87- as described on CODE CONTROL MODULE (FUNCTION 07) . If 22°C (71°F) is always displayed after switching ignition off regardless of the last setting, check voltage supply to -E87- (terminal 30) using wiring diagram. The display of A/C control head -E87- (and exterior temperature display in instrument cluster) for version up to index "K" can be changed from °C to °F and vise versa by pressing the "Temperature + left" (driver-side) with "circulating air button" pressed. The unit of display (°C or °F) for A/C control head -E87- as of index "M" is determined via the adaptation of the control module in instrument cluster (and transmitted to -E87- via the databus-system). -E87- can be operated for a certain time (up to about 30 minutes) after switching off the ignition by pressing the "Rest" button (residual heating). Operating time depends on charge condition of battery maximum about 10 minutes. For vehicles with Nippondenso compressor only A/C control heads beginning with Index "C" are to be or will be installed. If -E87- remains in operation after switching off the ignition, test cable connection to connector E terminal 7 for short circuit to positive (connection for auxiliary heating mode not foreseen for USA/Canada) using wiring diagram.

Scheme 54

1. Remove center part of instrument panel See «INSTRUMENT PANEL»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .
2. Press tabs to unlock and disconnect connectors (arrow).
3. Remove 4 screws -A-.

Note. If it is not possible to remove the A/C control head from center of instrument panel after removing the screws; remove wood trim from center part of dash.

Changes to model year 2000 vehicles

Note. When replacing A/C control head note allocation. See SYSTEM CHANGES FROM M.Y. 2000 (WITH REVISED DRIVER'S INFORMATION DISPLAY). . Illumination of display field and operating buttons occurs via A/C control head with part number beginning with index letter "M" through light emitting diodes (LEDs not replaceable). During malfunction test of temperature sensor -G56- intake screen of trim should not be closed.

Scheme 55

For A/C control head with part numbers beginning with Index "M"

1. Removing

1. Remove instrument cluster air outlet, center. See «CENTER AIR OUTLET IN INSTRUMENT PANEL, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__center-air-outlet-in-instrument-panel) .
2. Remove trim -A- for center instrument cluster. See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .
3. Remove radio or radio navigation system. See «RADIO, TELEPHONE, NAVIGATION, TRIP COMPUTER»(/audi/a8/d2-1994-1999/remont/communication-devices/#radio-telephone-navigation-trip-computer) .

Note. Different versions of trim -A- and A/C control head for vehicles with radio and with radio navigation system (or radio with greater service area). Different versions of A/C control head for vehicles with or without heated seats.

Scheme 56

Scheme 57

Scheme 58

Scheme 59

1. Unscrew 4 bolts -A-.
2. Press connector lock (arrow) back and remove connector.
3. Disconnect connector for rear window defroster and remove.
4. Remove switch for heated seat, press tabs -A- back and remove switch -B- to the back out of A/C control head - E87-.

Note. Illumination of display field and operating buttons occurs via A/C control head with part number beginning with index letter "M" through light emitting diodes (LEDs not replaceable). Different versions of -E87- are available (depending on the vehicle equipment e.g. with or without opening for the heated seat switch) as replacement parts. Installing

Installation is in reverse order of removal.

Scheme 60

1. Remove A/C control head. See «A/C CONTROL HEAD -E87-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-control-head-e87-removing-and) .
2. Remove screws -A- and carefully pry off control head panel.
3. Unscrew faulty bulb -B- approx. 90° (1/4 turn) and remove.

Checking

1. Remove side trim of center console on driver or front passenger side, respectively. «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .

Scheme 61

1. The cross-section of the condensation drain hose must not be constricted by the insulation mat. It must be possible to fit the hose onto the connection of the air conditioner housing without any stress. Re-position insulation mat, if necessary.
2. The condensation drain hose must be properly seated on the connection for the condensation outlet at the air conditioner housing (secure with hose tie, if necessary).
3. When installed, the condensation drain valve -A- must not be touching the heat deflector plate (when valve removed, check whether sufficient clearance exists between the floor panel of the center tunnel and the heat deflector plate).
4. The condensation drain valve must not be sticking as a result of wax or underbody sealant and must close properly.
5. If complaints are received regarding moisture in passenger compartment, use a wire to check whether condensation outlets of A/C system are soiled and clean, if necessary.

Note. If complaints are received regarding moisture in passenger compartment, check the drain hose -A-, the relevant valve -B- and the area below the air conditioner housing -C- for soiling. Remove electronics box-plenum if necessary; illustration shows drain hose on removed components. (Scheme 78)

Scheme 62

1. Remove side trim of center console on driver and passenger side, respectively.
2. Remove condensation drain hose from air conditioner housing and pull out of the center tunnel.

Note. Push condensation drain valve -A- through the floor panel of the center tunnel. Lock rib -B- fully in the panel of the center tunnel.

Scheme 63

Heater cores, removing and installing

Note. From November 2000, a running change in production led to a modified A/C housing. Revised heater cores (version "2") and changed coolant lines to heater cores are installed on this A/C housing. Changed heater cores have different dimensions, so that the fitting in the A/C housing also had to be changed. The A/C housing with version "2" heater cores can be identified from the outside via the coolant lines to the heater core

Scheme 64

1. The coolant lines for version "1" are inserted into the heater core from the front.
2. Coolant lines -A- and -B- for version "2" are inserted into the heater core -C- from the side.

Special tools and equipment

1. Hose clamps 3093 or 3094
2. VAG1306 drip tray
3. Compressed air gun, standard

See PASSENGER-SIDE HEATER CORE, REMOVING AND INSTALLING .

See DRIVER-SIDE HEATER CORE, REMOVING AND INSTALLING .

Passenger-side heater core, removing and installing

1. Determine coding for anti-theft radio.

1. Switch ignition off and disconnect battery ground strap.
2. Remove cowl panel. See «WIPER/WASHER SYSTEMS»(/audi/a8/d2-1994-1999/remont/wiperwasher-systems/#wiperwasher-systems) (1997-99), or «WINDSHIELD WIPER SYSTEM, SERVICING»(ref-196903-S19054507702005101000000) (2000-2003).

Scheme 65

Scheme 66

Scheme 67

1. Release pressure in cooling system by opening the cap on the coolant expansion tank and drain cooling system into a clean container. See «COOLING SYSTEM, DRAINING AND FILLING»(ref-196862-S32357803552005100900000) (1997-99), or «COOLING SYSTEM, DRAINING AND FILLING»(ref-196866-S33984552662005100900000) (2000-2003).
2. Disconnect both coolant hoses from the engine to the pump valve unit (-A- and -B-) and mark arrangement of coolant hoses.
3. Hold coolant hose -A- into clean container. (Scheme 82)
4. Carefully blow the coolant out of the pump valve unit and heater cores through coolant hose -B- with a compressed air. NOTE: Plug the upper coolant hose to each of the two heater cores alternately to make sure that the coolant is blown out of both heater cores.
5. Unplug harness connectors to the pump valve unit.
6. Remove reinforcing plate (plenum). See «REINFORCING PLATE (PLENUM), REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
7. Loosen securing screw -A- for the holder for coolant hoses (in plenum) about 2 turns.
8. Remove coolant line bracket.
9. Remove glove box and side trim of the center console. See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim).
10. Remove footwell air outlet.
11. Cover over floor of car and area below heater core with absorbent paper.
12. Lightly cover contact surface of both coolant lines -A- and -B- at grommet -C- with silicone lubricant (so that the lines can be moved without changing the position of the grommet).

Version "1" heater core, removing

1. Remove clip -A- and -B- and push the two coolant hoses in the direction of plenum.

Note. Since the grommet in the area of passage of the coolant lines is slightly covered with silicone lubricant, the lines can be moved without moving the grommet from the A/C housing.

Scheme 68

1. Remove screws -C- and remove bow.
2. Remove heater core from heating system.

Version "2" heater core, removing

1. Remove clamps -A- and -B-. (Scheme 86)
2. Remove both coolant lines from heater core.
3. Push both coolant lines in direction of "plenum chamber".

Note. Since the grommet in the area of passage of the coolant lines is slightly covered with silicone lubricant, the lines can be moved without moving the grommet from the A/C housing.

Scheme 69

1. Remove bolts -C-. (Scheme 86)
2. Remove bracket.
3. Pull out heater core -D-.

Version "1" heater core, installing

Installation is reverse of removal, noting the following

Scheme 70

1. Before installing the heater core, check openings -A- of condensation water drain for soiling and clean if necessary.

Note. Condensation water drain valve must not be obstructed by wax or underbody sealer and must close properly. The drain openings in the illustration are depicted with the heater cores installed.

Cleaning

1. Removed: Reach through opening in the heater core and clean the condensation water drains, for example, using wire.
2. Heater core installed: Clean condensation water drains from the outside, for example, using wire (with condensation water hose removed).

Scheme 71

1. Secure all connections using clamps appropriate for the model type
2. Always replace gaskets and sealing rings -D-. (Scheme 88)
3. Lightly cover sealing ring -D- with coolant.
4. Check coolant system for proper seal before installing glove compartment: See «COOLING SYSTEM, DRAINING AND FILLING»(ref-196862-S32357803552005100900000) (1997-99), or «COOLING SYSTEM, DRAINING AND FILLING»(ref-196866-S33984552662005100900000) (2000-2003).
5. Check position of the grommet in the opening of the coolant lines to plenum chamber before installing the glove compartment and the plenum chamber cover.

Note. Coolant pump -V50- of pump-valve unit must only be operated after the coolant circuit has been vented. Dry operation of the pump-valve unit leads to destruction.

1. Connect 2-pin harness connector to pump-valve unit only after venting the coolant circuit: See «COOLING SYSTEM, DRAINING AND FILLING»(ref-196862-S32357803552005100900000) (1997-99), or «COOLING SYSTEM, DRAINING AND FILLING»(ref-196866-S33984552662005100900000) (2000-2003).

Version "2" heater core, installing

1. Before installing the heater core, check openings -A- of condensation water drain for soiling and clean if necessary.

Scheme 72

Note. Condensation water drain valve must not be obstructed by wax or underbody sealer and must close properly. The drain openings in the illustration are depicted with the heater cores installed.

1. Removed: Both drain openings can be checked and if necessary cleaned via the opening for the heater core, using an illuminated angled mirror.
2. Heater core installed: Clean (with condensation water hose disconnected) condensation water drains from the outside, e.g. using wire. Installation is reverse of removal, noting the following
3. Secure all connections with clamps appropriate for the model type, or with the clamping brackets approved for this connection

Note. Clamps -A- and -B- can only be mounted with difficulty in installed position. (Scheme 90) To be able to replace the heater core in customer service with the A/C housing installed, clamping brackets -A- and -C- must be used. (Scheme 91)

Scheme 73

Scheme 74

Scheme 75

Scheme 76

1. Check both coolant lines -B- and the connections at heater core -C- for damage or soiling. (Scheme 92) NOTE: Sealing rings must always be replaced.
2. Lightly cover sealing ring -A- with coolant and install it onto coolant line -B-.
3. Place clamping bracket -A- (with studs) according to illustration onto connection at heater core -B-. (Scheme 93)
4. Place clamping bracket -C- (with holes) onto coolant line -D- according to illustration. (Scheme 93)
5. Insert coolant line -D- (with sealing ring) into connection of heater core -B-. (Scheme 93)
6. Secure coolant line with the two clamping brackets -C- and -D- in heater core. (Scheme 94)
7. Tighten both hex nuts -A- and -B- alternating and uniformly (tightening torque 3 Nm).

Scheme 77

Note. Clamping brackets -C- and -D- must be installed as illustrated (observe outer contour). (Scheme 94) Make sure clamping brackets are not canted when tightening hex nuts. Check the position of the clamping brackets after securing coolant lines, they must not contact other components.

1. Install the second coolant line in the same manner.
2. Check coolant system for proper seal before installing glove compartment: See «COOLING SYSTEM, CHECKING FOR LEAKS»(ref-196866-S10978658902005100900000) .
3. Check position of the grommet in the opening of the coolant lines to plenum chamber before installing the glove compartment and the plenum chamber cover.

Note. Coolant pump -V50- of pump-valve unit must only be operated after the coolant circuit has been vented. Dry operation of the pump-valve unit leads to destruction.

1. Connect 2-pin harness connector to pump-valve unit only after venting the coolant circuit: See «PRESSURE RELIEF VALVE IN FILLER CAP, CHECKING»(ref-196866-S37562489992005100900000) .

Driver-side heater core, removing and installing

1. Determine coding for anti-theft radio.

Scheme 78

1. Switch ignition off and disconnect battery ground strap.
2. Remove windshield wipers complete See «WIPER/WASHER SYSTEMS»(/audi/a8/d2-1994-1999/remont/wiperwasher-systems/#wiperwasher-systems) (1997-99). or «WINDSHIELD WIPER SYSTEM, SERVICING»(ref-196903-S19054507702005101000000) (2000-2003).
3. Remove passenger-side heater core. See «PASSENGER-SIDE HEATER CORE, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__passenger-side-heater-core-removing-and-installing). WARNING: The cooling system is pressurized when the engine is warm. Wear gloves and other appropriate protection, and slowly and carefully release system pressure, if necessary, before performing repairs.
4. Remove driver-side shelf and side trim of center console. See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim).
5. Loosen screws at clips -A- and -B- for coolant hoses each about 2 turns. (Scheme 95)
6. Lightly cover contact surface of both coolant lines at both grommets -C- and -D- with silicone lubricant (so that the lines can be moved without changing the position of the grommet).
7. Remove footwell air outlet.
8. Cover floor carpet in area below heater core with leak-proof foil and absorbent paper.

Scheme 79

1. Remove clamp -A- and -B-.
2. Push both coolant lines in direction of "plenum chamber". NOTE: Since the grommet in the area of passage of the coolant lines is slightly covered with silicone lubricant, the lines can be moved without moving the grommet from the A/C housing.
3. Slide out heater core in direction of passenger-side (perpendicular through A/C housing).

Scheme 80

1. Remove clamp -A- and -B-.
2. Disconnect coolant lines -C- and -D- from heater core -E-.
3. Slide out heater core in direction of passenger-side (perpendicular through A/C housing).

Installation is reverse of removal, noting the following

Scheme 81

1. Always replace gaskets and sealing rings -D-.
2. Slide heater core perpendicularly through the A/C housing from the passenger-slide.
3. Further work steps for installation. See «VERSION "1" HEATER CORE, INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__version-1-heater-core-installing) .

Installation is reverse of removal, noting the following

1. Slide heater core perpendicularly through the A/C housing from the passenger-side.

Note. Sealing rings must always be replaced. It makes sense to insert the heater core for passenger-side into A/C housing and to secure the bracket with bolt -C-, so that the heater core does not slide back into the A/C housing. (Scheme 99)

Scheme 82

Scheme 83

1. Check position of the grommets -C- and -D- in opening of the coolant lines to plenum chamber before installing the glove compartment and the plenum chamber cover.
2. Further work steps for installation. See «VERSION "2" HEATER CORE, INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__version-2-heater-core-installing) .

Flap and vent motors, servicing

Note. Mark connector for the motor when removing (danger of swapping with connectors of the other actuator motors). For the malfunction "adaptation limit exceeded", check connector at motor, there must be no play between the shaft of the actuator motor and the connector. Replace the actuator motor if it makes clicking or rattling noises in regular intervals (approx. every 7 minutes).

Scheme 84

Scheme 85

1. These noises originate via activation of the actuator motor via the A/C control head -E87- in actuator motor drive.
2. Activation occurs to maintain the flap/motor securely in one position.
3. To determine which actuator motor is making the noises, the different actuator motors must be connected in sequence (using VAG1598 test box and cables from VAG1594A connector test kit) to the 12 V supply voltage (B+ socket "E5" and Ground socket "E9") until a stop has been reached. (To reach the other stop, B+ and Ground (GND) must be swapped). The respective sockets from test box to the different actuator motors. See «TEST STEP 6 - MOTORS IN PASSENGER COMPARTMENT»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters), Electrical test, test step 6.3 to 6.10. Also see SYSTEM WIRING DIAGRAMS. NOTE: With gradual implementation, only actuator motors with an additional bolt -C- at housing are supplied as replacement parts. (Scheme 101)
4. This bolt is supposed to prevent cover -B- from lifting off and for the drive shaft in housing -A- to skip. (Scheme 101)
5. It may be necessary to remove bolt -C-, depending on the installation position of the actuator motor (the function is then performed by the bolt with which the actuator motor is bolted to the A/C housing).
6. Depending on the installation position of the actuator motor at A/C system, it may be necessary to shorten the rib of the third take-up point at A/C system in such a way that the actuator motor can be installed without bolt -C- or nut -D- making contact (in this case the actuator motor is not bolted on). (Scheme 102)
7. If an actuator motor is supplied as a replacement part, bolt -C- (M3 x 30) can be retrofitted with an appropriate shim washer -E- and nut -D-.

Left center vent motor -V110- and right center vent motor -V111-, removing and installing

Note. Mark connector for the motor when removing (danger of swapping with connectors of the other actuator motors).

Scheme 86

1. Remove instrument panel See «INSTRUMENT PANEL»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim). NOTE: Illustration shows vent motor -V111-. (Scheme 103)
2. Remove 2 screws -A-.
3. Remove vent motor. NOTE: Before installing the vent motor, check mounting of the flap (knob -C- must be located between the stops -B-). (Scheme 103) If the shaft of the motor is located in such an unfavorable position that it is not possible to install the motor
4. Connect vent motor (via a 5A fuse) to a 12V battery (terminal 4 and terminal 5.
5. Run servo motor as needed, until a suitable installation position is reached (use adapter cable set VW1594). Direction of rotation can be reversed by switching positive (+) and negative (-) leads. Tighten securing screws -A- only by hand, tightening torque 4 Ncm (0.35 in. lb). (Scheme 103) After installing, always check DTC memory. See «DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__diagnostic-trouble-code-dtc-memory-checking).

Center vent adjusting motor -V102-, removing and installing

Note. Mark connector for the motor when removing (danger of swapping with connectors of the other actuator motors).

Scheme 87

1. Remove driver-side shelf and side trim of center console See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim).
2. Remove 2 screws -A-. (Scheme 104)
3. Remove motor from air conditioner housing.

Note. Before installing the servo motor, check mounting of the flap (knob -C- must be located between the stops -B-). (Scheme 104) If the shaft of the servo motor is located in such an unfavorable position that it is not possible to install. See Notes regarding installation. See LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING. After installing, always check DTC memory. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02). Tighten securing screws -A- only by hand, tightening torque 4 Ncm (0.35 in. lb). (Scheme 104)

Defroster flap motor -V107-, removing and installing

Note. Mark connector for the motor when removing (danger of swapping with connectors of the other actuator motors).

Scheme 88

1. Remove driver-side shelf and side trim of center console See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .
2. Remove footwell air outlet.
3. Remove 2 screws -A-.
4. Remove flap motor (linkage -B- with lever remains connected to air conditioner housing).

Note. If the shaft of the flap motor is located in such an unfavorable position that it is not possible to install motor. See Notes regarding installation. See LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING . After installing, always check DTC memory. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02) . Tighten securing screws -A- only by hand, tightening torque 4 Ncm (0.35 in. lb).

Left footwell flap motor -V108- and rear footwell vent motor -V112-, removing and installing

Note. Mark connector for the motor when removing (danger of swapping with connectors of the other actuator motors).

1. Remove driver-side shelf and side trim of center console See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim).
2. Remove 2 screws -A- (motor -V108-) or 2 screws -B- (motor -V112-). (Scheme 106)
3. Remove motor.

Note. Before installing the motor, check mounting of the flap (knob -C- must be located between the stops -D-). (Scheme 106) If the shaft of the motor is located in such an unfavorable position that it is not possible to install motor. See Notes regarding installation. See LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING. After installing, always check DTC memory. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02). Tighten securing screws -A- and -B- only by hand, tightening torque 4 Ncm (0.35 in. lb). (Scheme 106)

Temperature regulator flap motor -V68- and right footwell flap motor -V109-, removing and installing

Note. Mark connector for the motor when removing (danger of swapping with connectors of the other actuator motors).

1. Remove glove box and side trim of center console See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim).
2. Remove footwell air outlet.
3. Remove 2 screws -A- (servo motor -V68-) or 2 screws -B- (servo motor -V109-). (Scheme 107)
4. Remove motor.

Scheme 89

Note. Before installing the servo motor -V109-, check mounting of the flap (knob -D- must be located between the stops -E-). (Scheme 107) When installing the servo motor -V68-, check that the relay lever -C- is correctly located. (Scheme 107) Tighten securing screws -A- and -B- only by hand, tightening torque 4 Ncm (0.35 in. lb). (Scheme 107) If the shaft of the flap motor is located in such an unfavorable position that it is not possible to install motor. See Notes regarding installation. See LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING. After installing, always check DTC memory. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02).

Instrument panel interior temperature sensor -G56-, removing and installing

1. Remove center part of instrument panel complete See «INSTRUMENT PANEL»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .

Note. The intake shaft -A- must not be closed. The temperature sensor -B- is not detachable from the switch mount, replace complete assembly. If incorrect measurement exists, test interior temperature sensor fan -V42- and relevant suction hose -C-.

Scheme 90

Center air outlet in instrument panel, removing and installing

1. Use special tool -C- insert into holes -D- and pull the center air outlet evenly out of center part of instrument panel.

Note. Test potentiometer -A- and switch -B-, connect scan tool and begin OBD program. (Scheme 109) See VAG 1551 ((VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS. Special tools -C- should not get caught on the fins of the outlet (they could break off). (Scheme 109)

Scheme 91

Making special tool

1. Bend wire (3 mm diameter) as shown. Size x = 6 mm (0.24)

Note. For removing the instrument panel air outlet.

Scheme 92

Scheme 93

1. Remove glove box or shelf on driver side, respectively See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .
2. Remove screw -A-.
3. Use special tool to pull air outlet out of instrument panel.

Scheme 94

1. Remove lower air outlet in right or left of instrument panel.
2. Loosen screw -A-.
3. Pull the outlet out of the instrument panel.

Side window air outlet in right (left) of instrument panel, removing and installing

1. Remove screw -A-.
2. Pull air outlet out of the instrument panel.

Note. Should the screw -A- not be installed, the air outlet is clipped into the instrument panel.

Scheme 95

Scheme 96

1. Carefully pry off cover -A-.
2. Remove screw -B-.
3. Remove photo sensor.

Scheme 97

1. Remove driver-side shelf or glove box and side trim of center console, respectively See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .
2. Remove air outlet in driver or passenger footwell, respectively.
3. Turn sensor -A- through about 90° (1/4 turn) and remove.

Note. Illustration shows right vent temperature sensor -G151-.

Scheme 98

1. Remove driver-side shelf and side trim of center console See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim) .
2. Remove 3 screws -A-.
3. Disconnect suction hose -B- and remove blower.

Note. Test operation. See OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03) . Check suction hose -B-; air flow must not be restricted and must be reliably installed onto the connection to the temperature sensor.

Scheme 99

1. Carefully pry off trim panel -A-.
2. Remove screws -B-.
3. Remove air outlet.

Climate Control Components in passenger compartment, updates from m.y. 2000

Note. Only components affected by updates to the climate control system and driver's information display from m.y. 2002 are listed below. Information for components not listed here remains unchanged up to m.y. 2000. See AUTOMATIC CLIMATE CONTROL COMPONENTS IN PASSENGER COMPARTMENT, SERVICING .

Note. The following list refers to items in (Scheme 118).

1. A/C kick-down switch - F46- No longer provided for vehicles with A/C control head -E87- with part number beginning with index letter "M"
2. A/C control head -E87- Allocation. See «SYSTEM CHANGES FROM M.Y. 2000 (WITH REVISED DRIVER'S INFORMATION DISPLAY)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__system-changes-from-my-2000-with) . Removing and Installing: See «A/C CONTROL HEAD -E87-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-control-head-e87-removing-and) .
3. Instrument panel interior temperature sensor -G56- For vehicles with A/C control head -E87- with part number beginning with index letter "M".
4. Auto-Check-System Displayed temperature is directly calculated in the instrument cluster in vehicles with A/C control head -E87- with part number beginning with index letter "M".
5. Interior temperature sensor fan -V42- For vehicles with A/C control head -E87- with part number beginning with index letter "M"

Scheme 100

Air distribution, schematic diagram

Note. For locations of individual components, see AUTOMATIC CLIMATE CONTROL COMPONENTS IN ENGINE COMPARTMENT, SERVICING .

Note. The following lists refers to items in (Scheme 119).

1. Engine compartment (plenum)
2. Passenger compartment
3. Air conditioner

1. Dust and pollen filter Installed in front flap
2. Fresh air blower -V2
3. Evaporator

1. D1 - Left heater core (driver side)
2. D2 - Right heater core (passenger side)
3. E1 - Left mixing chamber
4. E2 - Right mixing chamber
5. F - Air guide to center air outlet at rear
6. G1 - To left footwell air outlets Driver and rear footwell
7. G2 - To right footwell air outlets Passenger and rear footwell
8. H1 - To left instrument panel air outlet and to B-pillar left air outlet
9. H2 - To right instrument panel air outlet and to B-pillar right air outlet
10. J - To defroster outlets
11. K - To center instrument panel air outlet
12. L - Air intake duct for recirculating air mode

1. Air flow flap motor -V71- Flap closes completely in recirculating air and ACF mode and also partially at higher speeds (program controlled)
2. Recirculation flap motor -V113- Flap opens in recirculating air mode
3. Center vent adjusting motor -V102- Flap can be opened or closed by adjusting potentiometer in center air outlet -G142 (program-controlled) If flap is open, cold air is blended with air flowing out of center instrument panel outlets
4. Temperature regulator flap motor -V68- Flap can be opened or closed by adjusting center vent position sensor -G142- (program-controlled) If flap is closed, only cold air flows out of center instrument panel air outlets (see item 3)
5. Defroster flap motor - V107
6. Left footwell flap motor - V108
7. Right footwell flap motor -V109
8. Left center vent motor -V110
9. Right center vent motor -V111
10. Rear footwell vent motor -V112
11. ACF flap motor -V114- In preparation
12. Left vent temperature sensor -G150
13. Left vent temperature sensor -G150

Scheme 101

1. Radiator and condenser are clean (clean, if necessary)
2. Ribbed V-belt is in proper order and correctly tensioned
3. All air guides, covers and seals in proper order and correctly installed
4. Air flow through the two dust and pollen filters not restricted
5. The vehicle is not directly exposed to the sun's rays
6. Engine is at normal operating temperature With engine running, select the following A/C control head - E87- settings. "Auto" mode for driver and passenger sides "ECON" button not switched on (compressor switched on) "LO" temperature selection (driver and passenger sides)
7. A/C compressor is driven (the A/C clutch is switched on)
8. Radiator coolant fan -V7- runs (at least in stage 1).
9. Fresh air blower -V2- runs at maximum speed.
10. The air flow flap closes and recirculating air flap opens (about 1 minute after engine is started).
11. The coolant pump -V50- does not run.
12. Both left and right heat regulating valves (-N175- and - N176-) are closed (coolant hoses and coolant hoses to the heating system heater cores cool down).

Note. Testing heating performance of A/C system and operation of pump valve unit. See AUTOMATIC CLIMATE CONTROL SYSTEM HEATING PERFORMANCE AND OPERATION OF PUMP VALVE UNIT, TESTING . If one of the test requirements is not achieved, check DTC memory and perform output Diagnostic Test Mode (DTM). See OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03) .

Preparatory work

1. Check DTC memory, determine and repair any malfunctions which are displayed. See «DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__diagnostic-trouble-code-dtc-memory-checking) .
2. Perform basic setting. See «BASIC SETTING (FUNCTION 04)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__basic-setting-function-04) and check control head coding. See «CODE CONTROL MODULE (FUNCTION 07)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__code-control-module-function-07) .
3. Close front flap and sliding roof.
4. Measure ambient air temperature.
5. Close doors and windows.
6. Close left and right instrument panel air outlets.
7. Close B-pillar air outlets.

Note. The temperature of the air flowing out of the center instrument panel air outlets must be within the tolerance -C- of the diagram in (Scheme 120) after 5 minutes, depending on ambient temperature.

1. Temperature of air flowing out of the center instrument panel air outlets
2. Ambient temperature measured
3. Permissible temperature range for air outlet temperature

Scheme 102

1. Switch ignition on.
2. Open center instrument panel air outlets.
3. Position thumb wheel for temperature-controlled center outlet to "warm".
4. Set operating mode to "Auto" and "LO" temperature selection for driver and passenger sides on A/C control head - E87-.
5. Start engine (compressor is operated).
6. Run engine at 2000 RPM (start of time measurement).
7. Measure temperature of air flowing out of the center instrument panel air outlets (driver and passenger sides).

Compare measurements with the diagram.

Note. If the specified values are not achieved. See DETERMINING MALFUNCTION IF TEST RESULTS DIFFER FROM SPECIFICATIONS . It is good practice to use two separate thermometers for this measurement. The temperature of the air in the mixing chambers of the air conditioner housing (downstream of heater core) can be measured with VAG 1551 during the A/C system cooling performance test (Read measuring value block, function 08. See READ MEASURING VALUE BLOCK (FUNCTION 08) , display group 014).

Scheme 103

Scheme 104

1. To repeat A/C system cooling performance test, see «TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
2. For repairing possible malfunctions in refrigerant system, see «A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-checking-pressures) .

1. Test actuation of left and right heat regulating valves -N175- and -N176-, as well as coolant pump -V50-. See «AUTOMATIC CLIMATE CONTROL SYSTEM HEATING PERFORMANCE AND OPERATION OF PUMP VALVE UNIT, TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__automatic-climate-control-system-heating-performance) .

Scheme 105

1. To perform electrical test, see «AUTOMATIC CLIMATE CONTROL SYSTEM, ELECTRICAL TESTS»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
2. To repeat A/C system cooling performance test, see «TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .

1. Check DTC memory with VAG 1551 Scan Tool, determine and repair all the malfunctions displayed. See «DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__diagnostic-trouble-code-dtc-memory-checking) .
2. Erase DTC memory. See «DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, ERASING (FUNCTION 05)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
3. Start engine.
4. Read measured value block, function 08. See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) .
5. Select display group 001 and confirm entry with -Q- button.
6. Repeat cooling performance test. See «TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) and monitor display field 1 on VAG 1551.

Scheme 106

1. To read measuring value block, display group 001, see «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) .

Scheme 107

1. To check pressures in A/C refrigerant system, see «A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-checking-pressures) .
2. To perform A/C system cooling performance test, see «TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
3. To unplug connector to high pressure switch F23 and bridge connector terminals 1 and 2, see «A/C refrigerant high pressure switches -F23- and -F118»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .

1. Unplug connector from the A/C refrigerant low pressure switch - F73- and bridge the two terminals of the connector.
2. Check pressures in refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), CHECKING pressures»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-checking-pressures) .
3. Repeat A/C system cooling performance test. See «TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .

Scheme 108

1. To check pressures in A/C refrigerant system, see «A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-checking-pressures) .
2. To perform A/C system cooling performance test, see «TESTING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .

Automatic Climate Control System heating performance and operation of pump valve unit, testing

Note. This test covers the operation of the pump valve unit, as well as right and left heat regulating valves -N175- and - N176-, and coolant pump -V50-. If a difference from the specifications is found, perform electrical test. See AUTOMATIC CLIMATE CONTROL SYSTEM, ELECTRICAL . If there are complaints of heating system performance and if during testing, no malfunction of pump valve unit is found, check coolant hoses (from engine and from heater core to pump valve unit) for proper installation. See PUMP VALVE UNIT, REMOVING AND INSTALLING and COOLING SYSTEM, CHECKING FOR LEAKS .

1. The cooling system has been bled according to specifications. Checking: See «COOLING SYSTEM, DRAINING AND FILLING»(ref-196862-S32357803552005100900000) (1997-99), or «COOLING SYSTEM, DRAINING AND FILLING»(ref-196866-S33984552662005100900000) (2000-03).
2. All the air guides, covers and seals are in proper order and correctly installed.
3. Air flow through the two dust and pollen filters is not restricted.
4. The engine is at normal operating temperature, coolant temperature greater than 80° C (176° F).

1. Check DTC memory, determine and repair any malfunctions displayed. See «DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__diagnostic-trouble-code-dtc-memory-checking) .
2. Perform basic setting and check control head coding. See «CODE CONTROL MODULE (FUNCTION 07)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__code-control-module-function-07) .
3. Close front flap and sliding roof.
4. Close doors and windows.

1. Connect VAG 1551 Scan Tool. See «VAG 1551 ((VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters) .
2. Start engine and run at maximum cooling capacity for a few minutes (compressor is switched on, temperature selector at "LO" for left and right sides).
3. Switch ignition off.
4. Press "Rest" button (residual heating) on A/C control head - E87- A/C control head -E87- operates, coolant pump -V50- does not run, right and left heat regulating valves -N175- and - N176- closed NOTE: The time for the "Rest" function (residual heating) is limited by -E87- (to about 10 minutes).
5. Connect VAG 1551 and select Read measuring value block, function 08 (display group 014). See «READ MEASURING VALUE BLOCK (FUNCTION 08)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__read-measuring-value-block-function-08) .
6. Read off measured values of display fields 3 and 4. Specification: ambient temperature plus not more than 15 °C (59° F)
7. Set temperature selector for left side (on -E87-) to "HI". Specified values: Temperature reading of display field 3 increases to approx. engine temperature Coolant pump -V50- running, valve -N175- open and valve -N176- closed Temperature reading of display field 4 remains approximately constant. Temperature increase less than 10° C (50° F) and valve -N176- closed.
8. Set temperature selector for right side (at -E87-) to "HI". Specified values: Temperature reading of display field 4 increases to approx. engine temperature. Coolant pump -V50- running, valves -N175- and -N176- open
9. Set temperature selectors for left and right sides (at -E87-) to "LO". Specified values: Temperature reading of display fields 3 and 4 drop within 5 minutes to ambient temperature, plus no more than 15° C (59° F). Coolant pump -V50- is not running, valves -N175- and - N176- are closed

A/C refrigerant system (R-134a), components

HD = High-pressure side

ND = Low-pressure side

Note. Replacement A/C compressors supplied by Parts Dept. contain the total quantity of refrigerant oil for filling the refrigerant system: 250 cc (8.5 fl oz.) Testing A/C system cooling performance. See A/C REFRIGERANT SYSTEM, TESTING . Do not top-up refrigerant system by adding any refrigerant (drain system, evacuate and re-charge). O-ring diameters and tightening torques stated also apply to the threaded connections of the refrigerant line between individual components. Install only O-rings which are approved for R-134a refrigerant (identified by color coding, at present red or violet). Check pressures in the refrigerant system. See A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES . Servicing work on A/C system. See A/C SYSTEM REFRIGERANT SYSTEM, SERVICING .

Note. For vehicles with Nippondenso compressor, it may be necessary to blow compressed air and nitrogen through the refrigerant circuit between accumulator and compressor in the direction of flow of the refrigerant.

Note. The following list refers to items in (Scheme 127).

1. Compressor Remove refrigerant lines from Nippondenso compressor (with O-ring and tightening torques of fastening bolts). See «A/C REFRIGERANT LINES FROM NIPPONDENSO COMPRESSOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-lines-from-nippondenso-compressor) . Removing and installing: See «A/C COMPRESSOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-compressor-removing-and-installing) . NOTE: Removing and installing ribbed V-belt and checking alignment of belt pulleys See «RIBBED BELT, REMOVING AND INSTALLING»(ref-196865-S24437602202005100900000) . The piston stroke of compressor is variable and is set as a function of cooling performance required.
2. A/C compressor speed sensor -G111- Not applicable for vehicles with Nippondenso compressor
3. A/C clutch -N25
4. Oil drain plug 30 Nm (22 ft lb) Installed with sealing ring instead of O-ring Always replace sealing ring NOTE: Turn A/C compressor via A/C clutch in order to drain the oil faster.
5. Pressure relief valve O-ring: 8.8 * 1.9 mm 10 Nm (7 ft lb)
6. Connection with valve
7. A/C refrigerant high pressure switches -F23- and -F118
8. Condenser Intake connection: O-ring: 14.0 * 1.8 mm 30 Nm (22 ft lb) Outlet connection: O-ring: 10.8 * 1.8 mm 15 Nm (11 ft lb) Removing and installing: See «A/C CONDENSER, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-condenser-removing-and-installing) .
9. Cap with seal Always re-install over valve
10. Service connection For measuring, draining and re-charging
11. Threaded connection in refrigerant line O-ring: 10.8 * 1.8 mm 15 Nm (11 ft lb)
12. Restrictor Removing and installing: See «RESTRICTOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__restrictor-removing-and-installing) . Always replace restrictor (with O-ring) Coat O-ring with PAG oil before installing
13. Evaporator Removing and installing. See «A/C EVAPORATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-evaporator-removing-and-installing) . O-rings for A/C refrigerant lines: Intake: 10.8 * 1.8 mm Outlet: 17.2 * 1.8 mm O-rings (for refrigerant lines on evaporator intermediate piece): Intake and outlet: 13.4 * 2.4 mm Tightening torques: Central bolt (refrigerant lines at air conditioner housing): 25 Nm (18 ft lb) Bolts at evaporator: 5 Nm (44 in. lb)
14. A/C refrigerant low pressure switch -F73- NOTE: To test, bridge electrical connections in harness connector for removed A/C refrigerant low pressure switch -F73-. See «A/C REFRIGERANT LOW PRESSURE SWITCH -F73»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
15. Connection with valve For A/C refrigerant low pressure switch -F73- For measuring pressures
16. Accumulator O-rings: 17.2 * 1.8 mm 40 Nm (30 ft lb) Removing and installing: See «ACCUMULATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
17. Connection with valve Not applicable for vehicles with Nippondenso compressor
18. Cap Not applicable for vehicles with Nippondenso compressor

Scheme 109

Scheme 110

1. Remove front bumper See «BUMPER»(/audi/a8/d2-1994-1999/remont/exterior-body-panels/#bumper).
2. Remove left headlight. See «LIGHTS, SWITCHES - EXTERIOR»(/audi/a8/d2-1994-1999/remont/steering-column-switches/#lights-switches-exterior) (1997-99), or «LIGHTS, SWITCHES-EXTERIOR»(ref-196904) (2000-2003).
3. Unplug connector from the ABS hydraulic unit.
4. Discharge A/C refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-discharging).
5. Disconnect coolant hoses -A-. (Scheme 128)
6. Tightening torque: 40 Nm (30 ft lb)
7. Loosen hexagon nut -B-. (Scheme 128)
8. Remove hexagon nut -C-.
9. Pull accumulator forward and release from catch.

Note. Replace accumulator. See A/C REFRIGERANT SYSTEM (R-134A), REPLACING COMPONENTS . Tightening torques of refrigerant lines and O-rings. See A/C REFRIGERANT SYSTEM (R-134A), COMPONENTS . Removed accumulator contains refrigerant oil which must be restored to the refrigerant system (with the new accumulator). The quantity of oil can be correctly adjusted depending on the circumstances. If for example, the accumulator was only damaged in an accident (no refrigerant flowed out and no moisture or dirt got into the refrigerant system), the A/C system can be serviced without any extensive repair work simply by matching the weight of the old and new accumulators. Pour refrigerant oil into the new accumulator until it has reached the same weight of the damaged component.

Note. Beginning model year 1999, an accumulator will be phased into production with a block connection for A/C refrigerant lines -A- fastened to the accumulator. Tighten bolt -B- for this version to 20 Nm (15 ft lb).

Scheme 111

A/C condenser, removing and installing

1. Discharge A/C refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-discharging) .
2. Remove front bumper. See «BUMPER»(/audi/a8/d2-1994-1999/remont/exterior-body-panels/#bumper) .
3. Disconnect hydraulic oil cooler loop and swivel to the side.

Note. Tightening torques of refrigerant lines and O-rings. See A/C REFRIGERANT SYSTEM (R-134A), COMPONENTS . Replacing condenser. See A/C REFRIGERANT SYSTEM (R-134A), REPLACING COMPONENTS .

Restrictor, removing and installing

1. Remove plenum cover.
2. Discharge A/C refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-discharging).
3. Disconnect refrigerant line at the threaded connection -A- Tightening torque: 15 Nm (11 ft lb)
4. Use needle-nose pliers to pull restrictor -B- out of the refrigerant line. (Scheme 130)

Scheme 112

Note. Install restrictor -B- the right way round (arrow on restrictor faces toward evaporator). (Scheme 130) Make sure O-ring -C- is correctly located in the groove. (Scheme 130) The restrictor must be seated free of play in the refrigerant line. Lubricate O-ring lightly (of restrictor) before installing in refrigerant line. (Scheme 130) Replace O-ring -D-.

A/C refrigerant lines from Nippondenso compressor, removing and installing

1. Discharge A/C refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-discharging).
2. Remove bolts -A- and -B-. see scheme 131
3. Tightening torque: 25 Nm (18 ft lb)
4. Replace O-rings. -C- (23.8 * 2.4mm) and -D- (11.1 * 1.8 mm)

Scheme 113

Note. O-rings may not be used again.

A/C compressor, removing and installing

1. Discharge A/C refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-discharging) .
2. Remove compressor from mounting bracket. See «A/C COMPRESSOR FROM MOUNTING BRACKET, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-compressor-from-mounting-bracket-removing) .
3. Disconnect refrigerant lines from the compressor (tightening torques and O-rings. See «A/C REFRIGERANT SYSTEM (R-134A), COMPONENTS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-components) .

Note. If a compressor is to be shipped for quality monitoring, connections should be sealed with caps. Replace compressor. See A/C REFRIGERANT SYSTEM (R-134A), REPLACING COMPONENTS . When first operating compressor, start engine with compressor switched off ("OFF" mode). Wait until the idle speed has stabilized before switching the compressor on and then run at idle for at least 10 minutes. Removing and installing ribbed V-belt. See RIBBED BELT, REMOVING AND INSTALLING .

A/C evaporator, removing and installing

Note. From November 2000, a running change in production led to a modified A/C housing. A revised evaporator (version "2") and changed refrigerant lines to evaporator are installed on this A/C housing. Changed evaporator has different dimensions, so that the fitting in the A/C housing also had to be changed. The A/C housing with version "2" evaporator can be identified from the outside via the coolant lines to the heater core. See HEATER CORES, REMOVING AND INSTALLING . Version "2" A/C housings up to January of 2001 are supplied with an evaporator with glued foam seal. As of January of 2001, the seal at evaporator will be implemented in a running change to an annular rubber seal.

Removing

1. Discharge A/C refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-discharging).
2. Remove reinforcing plate (plenum). See «REINFORCING PLATE (PLENUM), REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
3. Remove fresh air blower -V2-. See «FRESH AIR BLOWER -V2-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
4. Remove cover with recirculating air flap.
5. Remove 3 screws -A- and pry off clips -B-. see scheme 132
6. Remove holders for refrigerant lines -C- and -D-.

Scheme 114

Note. Screw -D- is not easily installed on vehicles with reinforcing plate (plenum) after installing the cover for the evaporator.

Scheme 115

1. With cover removed, locate and install a suitable washer -B- on screw -A-.
2. Tighten screw -A- 2 turns. see scheme 133
3. Install cover.
4. Rework hole in bracket -C- into a slit -D
5. Protect reworked areas -D- with corrosion protection.
6. Install bracket -C- per see scheme 133.
7. Remove cover for evaporator.

Scheme 116

1. Separate threaded connection -A- in the refrigerant line. Tightening torque: 15 Nm (11 ft lb)
2. Remove screw -B-. see scheme 134 Tightening torque: 25 Nm (18 ft lb)
3. Disconnect refrigerant lines from the evaporator. NOTE: Replace O-rings -C- and -D-. See «A/C REFRIGERANT SYSTEM (R-134A), COMPONENTS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-components).
4. Remove screws -A-. see scheme 135 Tightening torque: 5 Nm (44 in. lb)
5. Remove connection piece -C-.

Scheme 117

Note. Replace O-rings -B-. See A/C REFRIGERANT SYSTEM (R-134A), COMPONENTS. see scheme 135 When installing, make sure that the grommet -D- is correctly located. see scheme 135

1. Remove evaporator.

Note. Replacing evaporator. See A/C REFRIGERANT SYSTEM (R-134A), REPLACING COMPONENTS. Before installing the evaporator, check both condensation drain openings -A- and clean, if necessary. see scheme 136

Scheme 118

Removing version "2" evaporator

1. Remove bolts -A-. see scheme 137
2. Remove connecting line -B-.
3. Remove evaporator.

Installing

Installation is reverse of removal, noting the following

Scheme 119

1. Replace O-ring seals -C- and -D- between connecting line in A/C housing -B- and to evaporator -E-. see scheme 138 Bolt -A- tightening torque: 3 Nm. see scheme 138 O-ring seals -C-Exit: 13.4 mm/2.4 mm O-ring seals -D-Input: 11.2 mm/2.4 mm

Note. Ensure proper seating of the O-rings -C- and -D- in the groove of the connecting lines to evaporator -E-. Ensure proper seating of grommet -D- to A/C housing at connecting line for evaporator -C- (see illustration for version "1" V87-1603).

Scheme 120

Air conditioner housing, removing and installing

Note. As of November 2000, production will be switched gradually to a revised A/C housing (version "2'). Several components have been changed on this A/C housing, compared to version "1". The version "2" A/C housing can be identified from the outside via the coolant lines to the heater core for heater. See HEATER CORES, REMOVING AND INSTALLING . When removing, mark the different actuator motors and the respective connectors between flap and motor (danger of swapping with the connectors of other actuator motors). If connectors are swapped, the actuator motors with the incorrect connectors do no reach their specified end position, and the malfunction "adaptation limit exceeded" will be displayed in DTC memory after basic setting.

Scheme 121

Scheme 122

1. Discharge A/C refrigerant system. See «A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-discharging).
2. Cover driver and front passenger seat with protective covers.
3. Switch ignition on and press the "Def" button on -E87- (air flow of air conditioner to windshield, flaps for instrument panel air outlets closed).
4. Position power-operated seats so that the securing screws for the center console are accessible.
5. Determine coding for anti-theft radio. CAUTION: On vehicles equipped with Audi Telematics by OnStar(R), switch-off the emergency (back-up) battery for the Telematic/Telephone Control Module prior to disconnecting vehicle battery. See «ADAPTATION (FUNCTION 10)»(/audi/a8/d2-1994-1999/remont/communication-devices/#on-board-diagnostic-obd-radio-navigation-steering-telematics). After reconnecting vehicle battery, re-code and check operation of anti-theft radio. Also check operation of clock and power windows according to Repair Manual and/or Owner's Manual. After reconnecting vehicle battery on vehicles equipped with Audi Telematics by OnStar(R), switch-on the emergency (back-up) battery for the Telematic/Telephone Control Module. See «ADAPTATION (FUNCTION 10)»(/audi/a8/d2-1994-1999/remont/communication-devices/#on-board-diagnostic-obd-radio-navigation-steering-telematics).
6. Switch ignition off and disconnect battery ground strap
7. Remove instrument panel with center console and instrument panel mounting complete See «INTERIOR TRIM»(/audi/a8/d2-1994-1999/remont/gauges-instrument-panels/#interior-trim).
8. Remove control module for airbag.
9. Remove bracket -A-.
10. Remove cover with air flow flap. See «COVER WITH AIR FLOW FLAP, REMOVING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
11. Disconnect all air guides to the air conditioner housing.
12. Remove cowl panel and windshield wipers complete. See «WIPER/WASHER SYSTEMS»(/audi/a8/d2-1994-1999/remont/wiperwasher-systems/#wiperwasher-systems) (1997-99), or «WINDSHIELD WIPER SYSTEM, SERVICING»(ref-196903-S19054507702005101000000) (2000-2003).
13. Remove reinforcing plate (plenum). See «REINFORCING PLATE (PLENUM), REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
14. Release pressure in cooling system by opening cap to coolant reservoir, drain cooling system into a clean container. WARNING: The cooling system is pressurized when the engine is warm. Wear gloves and other appropriate protection, and slowly and carefully release system pressure, if necessary, before performing repairs.
15. Unplug connectors to the pump valve unit.
16. Disconnect both coolant hoses from engine to pump valve unit (-A- and -B-) and mark installation position of hoses. see scheme 142
17. Hold coolant hose -A- in a container. see scheme 142
18. Remove plenum cover and cover for electronic box.
19. Carefully blow coolant out of the pump valve unit and heater cores through the coolant hose -B- with compressed air. NOTE: Pinch off upper coolant hose to each of the two heater cores alternatively so that the coolant is blown out of both heater cores.
20. Mark coolant hoses -A- and -B- and disconnect from the pump valve unit to the heater cores at the coolant hoses. see scheme 143
21. Separate electrical connections to air conditioner housing (pay attention to Ground cable to A-pillar).
22. Disconnect condensation drain hoses from air conditioner housing.
23. Disconnect coolant hoses to the evaporator and seal. See «A/C EVAPORATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-evaporator-removing-and-installing).
24. Remove 4 securing screws -A- (in passenger compartment). see scheme 144
25. Remove 2 securing nuts -B- (in passenger compartment).
26. Remove air conditioner housing complete (to interior). CAUTION: Immediately plug open connections on A/C components and lines to prevent dirt and moisture contamination. Check that damper element -C- is correctly located. see scheme 144 Check coolant hoses to the heater cores (bottom hose = coolant supply, top hose = coolant return). Always replace gasket -A- (between plenum and air conditioner housing). see scheme 145 When installing the air conditioner housing, do not pinch the wiring to the servo motors (in plenum) and do not damage gasket -A- at the stay bolts. Connect coolant hoses to the engine correctly (pay attention to marking made). Coolant pump -V50- of pump valve unit must not be operated until after bleeding the cooling system (dry running causes damage to the pump). For this reason, do not plug in the 2-pin connector to the pump valve unit until after bleeding the cooling system.
27. Bleed cooling system See «COOLING SYSTEM, DRAINING AND FILLING»(ref-196862-S32357803552005100900000) (1997-99), or «COOLING SYSTEM, DRAINING AND FILLING»(ref-196866-S33984552662005100900000) (2000-2003).

1. Check that grommets for coolant hoses between engine compartment and plenum are correctly located after installation.
2. Check that condensation drain hoses are correctly located.

Air conditioner housing, disassembling and assembling

Note. For removing and installing air conditioner housing, see AIR CONDITIONER HOUSING, REMOVING AND INSTALLING .

Screen, fresh air blower, evaporator and covers in plenum, removing and installing

Note. Items 1 through 16 in the following list see scheme 146

Scheme 123

1. Self-tapping screw
2. Screen
3. Lever
4. Air flow flap motor -V71- Removing and installing. See «AIR FLOW FLAP MOTOR -V71-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__air-flow-flap-motor-v71-removing).
5. Cover
6. Bolt 8 Ncm (0.7 in. lb)
7. Fresh air intake duct temperature sensor -G89- Removing and installing. See «FRESH AIR INTAKE DUCT TEMPERATURE SENSOR -G89-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
8. Intake opening with air flow flap and seal Removing and installing. See «COVER WITH AIR FLOW FLAP, REMOVING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning). Disassembling and assembling. See «DISASSEMBLING AND ASSEMBLING INTAKE SHAFT»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__disassembling-and-assembling-intake-shaft).
9. Bracket For wiring harness
10. Housing for fresh air blower
11. Rings for air guide
12. Bracket For coupling
13. Self-tapping screw
14. Bracket For fresh air blower
15. Fresh air blower - V2- Removing and installing. See «FRESH AIR BLOWER -V2-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning).
16. Housing lower part with air distribution housing Disassembling and assembling. See «AIR CONDITIONER HOUSING (LOWER) AND AIR DISTRIBUTION HOUSING, DISASSEMBLING AND ASSEMBLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__air-conditioner-housing-lower-and-air). Air distribution housing, disassembling and assembling. See «AIR DISTRIBUTION HOUSING, DISASSEMBLING AND ASSEMBLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__air-distribution-housing-disassembling-and-assembling). Version "1" and "2" of A/C housing are different NOTE: Items 17 through refer to 29 see scheme 147.
17. Wiring harness for air conditioner housing Electrical connections to air conditioner housing.
18. Filler Securely bonded to lower part of housing
19. Control module for fresh air blower -J126- Removing and installing. See «CONTROL MODULE FOR FRESH AIR BLOWER -J126-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__control-module-for-fresh-air-blower).
20. Connector tubes with grommet Refrigerant lines between bolt location on housing and evaporator Grommet seals the bolt location with housing Version "1" and "2" of A/C housing are different
21. O-ring Always replace. See «A/C REFRIGERANT SYSTEM (R-134A), COMPONENTS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-components). Version "1" and "2" of A/C housing have different dimensions
22. Cylinder screw 25 Nm (18 ft lb)
23. Evaporator Removing and installing. See «A/C EVAPORATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-evaporator-removing-and-installing). Must only be removed with an empty refrigerant circuit Version "1" and "2" of A/C housing are different. See «A/C EVAPORATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-evaporator-removing-and-installing). Version "2" A/C housings up to January of 2001 are supplied with an evaporator with glued foam seal. As of January of 2001, the seal at evaporator will be implemented in a running change to an annular rubber seal.
24. Bolt
25. Tube bracket For coolant tubes to heater core, passenger side Removing and installing: See «PASSENGER-SIDE HEATER CORE, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__passenger-side-heater-core-removing-and-installing).
26. Cover for evaporator
27. Tube bracket For coolant tubes to heater core, driver side
28. Recirculation flap motor -V113- Removing and installing: See «RECIRCULATION FLAP MOTOR -V113-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__recirculation-flap-motor-v113-removing-and).
29. Cover with recirculating air flap Removing and installing: See «RECIRCULATION FLAP MOTOR -V113-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__recirculation-flap-motor-v113-removing-and). Disassembling and assembling: See «DISASSEMBLING AND ASSEMBLING COVER WITH RECIRCULATING AIR FLAP»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__disassembling-and-assembling-cover-with-recirculating).

Scheme 124

Disassembling And Assembling Cover With Recirculating Air Flap

1. Bolt
2. Air flap
3. Shaft
4. Bracket
5. Bolt
6. Connecting element
7. Cover

Scheme 125

Disassembling And Assembling Intake Shaft

1. Bolt
2. Air flap
3. Shaft
4. Bracket
5. Bolt
6. Intake shaft with seal (for hood)

Scheme 126

Air conditioner housing (lower) and air distribution housing, disassembling and assembling

Note. The following list refers to items in see scheme 150.

1. Air distribution housing Disassembling and assembling: See «AIR DISTRIBUTION HOUSING, DISASSEMBLING AND ASSEMBLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__air-distribution-housing-disassembling-and-assembling) . Version "1" and "2" of A/C housing are different (different heater cores. See «HEATER CORES, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__heater-cores-removing-and-installing) ).
2. Clip
3. Heater core Removing and installing, passenger side. See «PASSENGER-SIDE HEATER CORE, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__passenger-side-heater-core-removing-and-installing) Removing and installing, driver side: See «DRIVER-SIDE HEATER CORE, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__driver-side-heater-core-removing-and-installing) . Version "1" and "2" of A/C housing are different. See «HEATER CORES, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__heater-cores-removing-and-installing) .
4. Bracket Version "1" and "2" of A/C housing are different (different heater cores. See «HEATER CORES, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__heater-cores-removing-and-installing) ).
5. Self-tapping screw
6. Bracket For wiring harness
7. O-ring Always replace
8. Clamp Always replace Check for correct fit
9. Coolant tubes, passenger side With dual grommets Version "1" and "2" of A/C housing are different (different heater cores. See «HEATER CORES, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__heater-cores-removing-and-installing) ).
10. Coolant tubes, driver side With grommets Version "1" and "2" of A/C housing are different (different heater cores. See «HEATER CORES, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__heater-cores-removing-and-installing) ).
11. Coolant tube, driver side lower With grommets Version "1" and "2" of A/C housing are different (different heater cores. See «HEATER CORES, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__heater-cores-removing-and-installing) ).
12. Opening For wiring harness
13. Housing, lower part Version "1" and "2" of A/C housing are different (different evaporator. See «A/C EVAPORATOR, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-evaporator-removing-and-installing) ).
14. Insulation mat only installed on version "1" A/C housings glued together with complete surface of the lower part of housing, checking. Not planned for version "2" A/C systems
15. Seal Always replace
16. Screw
17. Tube bracket For coolant tube, driver side lower

Scheme 127

Air distribution housing, disassembling and assembling

Note. The following list refers to items in see scheme 151.

1. Air distribution housing Version "1" and "2" of A/C housing are different (different heater cores. See «HEATER CORES, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__heater-cores-removing-and-installing) ).
2. Seal
3. Seal
4. Self-tapping screw
5. Air guide with shut off flap to center outlet, right Right center vent motor - V111-, removing and installing: See «LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-center-vent-motor-v110-and)
6. Air guide with shut off flap to floor outlet, right For Right footwell flap motor -V109-, removing and installing, see «TEMPERATURE REGULATOR FLAP MOTOR -V68- AND RIGHT FOOTWELL FLAP MOTOR -V109-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__temperature-regulator-flap-motor-v68-and) .
7. Air guide with shut off flap to floor outlet, left For Left footwell flap motor - V108- removing and installing, see «LEFT FOOTWELL FLAP MOTOR -V108- AND REAR FOOTWELL VENT MOTOR -V112-, REMOVING AND INSTALLING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-footwell-flap-motor-v108-and) .
8. Air guide with shut off flap to center outlet, left For Left center vent motor - V110- removing and installing, see «Left center vent motor -V110- and right center vent motor -V111-, removing and installing»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__left-center-vent-motor-v110-and) .

Scheme 128

A/C refrigerant system (R-134a), leak testing

1. Use halogen leak detector Hitec HI400A-TEL or equivalent to check for refrigerant leaks.
2. Refrigerant gas dissipates very quickly. Avoid drafty or windy areas when checking for leaks.
3. Some refrigerant leaks are apparent by refrigerant oil deposits on or near leak location. Confirm by using leak detector.
4. If the refrigerant system is discharged (empty), charge system with approx. 100 g (3.5 oz.) of refrigerant in order to check for leaks.

Scheme 129

1. Check refrigerant system for leaks following leak detector manufacturer's instructions.
2. Check for refrigerant leaks by passing detector probe under suspected leaking components.

Note. See leak detector manufacturer instructions.

A/C refrigerant system (R-134a), testing with pressure gauges

Due to the constant temperature/pressure relationship of R-134a, approximate high side system temperature can be determined based on system pressure.

Pressure gauges may have one or more temperature scales in addition to the pressure scale. Since various refrigerants have different temperature/pressure relationships, each gauge is specific for a particular refrigerant.

Measuring pressure and temperature in a "switched-on" refrigerant system

Use the A/C refrigerant high pressure gauge to measure the high side system pressure between the compressor and restrictor (including condenser) with the A/C switched on.

The temperature display of the high pressure gauge applies only to a portion of the high pressure side. The high pressure gauge displays approximate temperature between the compressor outlet and restrictor.

Note. The temperature/pressure relationship only holds true when the refrigerant system contains liquid and vapor, but not when it contains only gas. In the gaseous state, the temperature is approx. 10-30°C (18-54°F) higher than indicated on the pressure gauge.

Measuring pressure and temperature in a closed container or "switched-off" refrigerant system

Due to the constant temperature/pressure relationship of R-134a, approximate temperature of refrigerant in a closed container or in a switched-off A/C system can be determined based on its pressure.

If temperature display on gauge is lower than the actual temperature of the refrigerant, the refrigerant container or system is empty (discharged).

Note. The temperature/pressure relationship only holds true when the refrigerant system contains liquid and vapor, but not when it contains only gas. In the gaseous state, the temperature is approx. 10-30°C (18-54°F) higher than indicated on the pressure gauge.

A/C refrigerant system (R-134a), checking pressures

Before checking refrigerant system pressures, check A/C system cooling performance. See A/C REFRIGERANT SYSTEM, TESTING .

Use high pressure service valve for checking system pressures.

1. Condenser and radiator clean and free of obstructions (clean if necessary)
2. Drive belts for compressor and Generator in good condition and properly tensioned
3. All air ducts, covers and seals OK and correctly installed
4. Check DTC memory using VAG 1551 Scan Tool and eliminate/repair any malfunctions indicated (not affecting A/C system)
5. All air distribution flaps reach end positions
6. Engine at normal operating temperature
7. Evaporator housing and heater box do not leak air (draw in secondary air) at high fresh air blower speed
8. Outside (ambient) temperature must be between 15° - 45°C (59° - 113°F)
9. Engine running and system set to maximum cooling ("Auto" operating mode with "LO" temperature setting selected)

1. Switch compressor ON (the warning light in the ECON button does not light up.
2. Temperature selection "LO" (for driver and passenger side).

If the compressor is activated (A/C clutch is switched ON)

1. Fresh air blower -V2- runs
2. Coolant fan -V7- runs (at least in stage 1)
3. Closes back pressure door and opens recirculation door (within 1 minute after starting vehicle)

Note. With open recirculation door air flows out of outlets in the instrument panel even though the back pressure door is closed. If the air comes out of the instrument panel outlets, left and right heat regulating valves -N175- and -N176- of pump unit are closed and coolant pump -V50- does not run (the heater cores are not warmed up).

If one of the requirements is not met, check DTC memory and repair any malfunctions. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02) .

Preparation work

1. Check DTC memory and determine and repair all possible malfunctions (See «DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02)»(/audi/a8/d2-1994-1999/remont/heated-glassdefoggers/#on-board-diagnostic-obd-hvac-can-defrosters__diagnostic-trouble-code-dtc-memory-checking) ).

1. Switch ignition OFF.
2. Connect high pressure hose of refrigerant recovery/recycling/recharging unit Kent-Moore ACR 4 , or equivalent, to high pressure service valve. See «HIGH PRESSURE SERVICE CONNECTION WITH SCHRADER VALVE»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__high-pressure-service-connection-with-schrader) .
3. Leave low pressure hose of refrigerant recovery/recycling/recharging unit disconnected.

Note. Only a high pressure service valve is used for A/C system servicing and checking pressures. A low pressure service valve is not installed in the A/C system. Perform all A/C system pressure checks through the high pressure service valve.

R134a TEMPERATURE AND PRESSURE RELATIONSHIP

If A/C refrigerant system base pressure is less than specified on chart, system is low on refrigerant

1. Check system for leaks using halogen leak detector Hitec HI400A-TEL or equivalent, repair system as necessary.
2. Check pressure relief valve on A/C compressor. If the pressure relief valve has blown
3. Check actuation of coolant fan according to wiring diagram.
4. Check for pinched, kinked or damaged refrigerant lines/hoses. If no problems are found
5. Discharge refrigerant system, then evacuate and recharge.

If A/C refrigerant system pressure corresponds to or is higher than base pressure specified on chart

1. Start engine.
2. Adjust A/C to maximum cooling. Compressor runs continuously. NOTE: If A/C clutch -N25- is not engaged, check voltage supply to A/C clutch according to wiring diagram. If voltage is OK, repair (replace) A/C clutch. See «A/C CLUTCH, SERVICING»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
3. Raise engine speed (RPM) to 2000.
4. Note pressure on A/C high pressure gauge. Specified high pressure value: High side (discharge) pressure increases from base pressure (engine OFF) to maximum 20 bar (290 psi)

Note. For switching pressure specifications of A/C refrigerant low pressure switch -F73-. See A/C REFRIGERANT LOW PRESSURE SWITCH -F73 and A/C refrigerant high pressure switch -F118-. See A/C REFRIGERANT HIGH PRESSURE SWITCHES -F23- AND -F118 .

Pressure in refrigerant circuit corresponds to chart or is higher

1. Start engine.
2. Adjust A/C to maximum cooling performance.

Note. If compressor is not activated, note test requirements.

Refrigerant R-134a

Note. When charging system on high pressure side, always use maximum amount of A/C refrigerant, as some refrigerant remains in hoses of refrigerant recovery, recycling and recharging unit. Since 11.97, valves with different size restrictors are installed (colored). Vehicles with change have 50g more refrigerant. Drilling of small valve is colored yellow for identification.

Refrigerant (PAG) oil

Note. The PAG oil used in refrigerant system Part No. G 052 300 A2.

AUDI A8 PAG OIL CAPACITY SPECIFICATION

Note. R-134a refrigerant oil (PAG oil) absorbs moisture very rapidly. Moisture combines with the refrigerant to form acids which will damage the system. Use only specified oil from a sealed container and ALWAYS reseal container immediately after use. DO NOT use oil if it has become contaminated with moisture or if oil container has been left open. Use only the specified synthetic oil (Polyalkylene Glycol or PAG) for the R-134a refrigerant system. Refrigerant oils used for R-134a and R-12 systems are NOT compatible. DO NOT use the oil for an R-12 system in an R-134a system. If refrigerant oils are mixed, the system will be contaminated and compressor failure may result. Use only approved refrigerant oils that have been released into the Audi parts system. Replacement A/C compressors supplied by the Parts Dept. are filled with 250 cc + 20 cc (8.5 fl oz. + 0.7 fl oz.) of refrigerant oil. This is the total A/C system refrigerant oil capacity. When A/C is switched on for the first time, the refrigerant oil is distributed throughout the entire system. When replacing A/C system components, add appropriate amount of refrigerant oil to component. See A/C REFRIGERANT SYSTEM (R-134A), REPLACING COMPONENTS . Dispose of used refrigerant oil following laws governing hazardous waste disposal.

A/C refrigerant system (R-134a), discharging

Note. Follow all safety measures starting under A/C REFRIGERANT SYSTEM (R-134A), SAFETY MEASURES when discharging an A/C refrigerant system.

Discharging

Make sure initial set-up has been performed on recovery/recycling/recharging unit before discharging A/C system.

Scheme 130

1. Connect red high pressure hose -A- of refrigerant recovery/recycling/recharging unit to high pressure service valve (fitting) on vehicle and open coupler valve.
2. Leave blue low pressure hose -B- of refrigerant recovery/recycling/recharging unit disconnected. NOTE: Only a high pressure service valve is used for A/C system servicing. A low pressure service valve is not installed in the A/C system. Perform all A/C system service operations (i.e. discharging, evacuating and charging) through the high pressure service valve only. CAUTION: Always follow manufacturer's instructions when using a refrigerant/recovery/recycling/recharging unit.
3. Following refrigerant recovery/recycling/recharging unit manufacturer's instructions, discharge A/C system into refrigerant recovery/recycling/recharging unit.
4. After emptying A/C system, disconnect power supply from A/C clutch -N25- (for example, unplug connector from A/C refrigerant low pressure switch -F73-) to prevent accidental compressor operation with A/C system discharged.

A/C refrigerant system (R-134a), evacuating & recharging

Note. Only a high pressure service valve is used for A/C system servicing. Perform all A/C system service operations (i.e. discharging, evacuating and recharging) through the high pressure service valve only.

Evacuating & recharging

Follow all safety measures under A/C REFRIGERANT SYSTEM (R-134A), SAFETY MEASURES when evacuating and recharging the A/C refrigerant system.

1. Follow refrigerant recovery/recycling/recharging unit manufacturer's instructions for evacuating and recharging A/C system.
2. Evacuate refrigerant system for a minimum of 30 minutes.
3. When recharging A/C system, add correct amount of refrigerant and PAG oil to system, see A/C refrigerant system capacities. See «A/C REFRIGERANT SYSTEM (R-134A), CAPACITIES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) .
4. After system recharge, manually rotate A/C compressor approx. 10 turns before starting engine. Start engine with A/C OFF. After idle speed has stabilized, switch A/C ON and let engine idle (compressor running) for a minimum of two minutes before raising engine speed.

A/C refrigerant system (R-134a), flushing with compressed air and nitrogen

1. Use compressed air and nitrogen (available locally) to remove moisture, impurities and old refrigerant oil from A/C refrigerant system.
2. First blow out old refrigerant oil and dirt with compressed air, then dry components with nitrogen.
3. DO NOT blow compressed air and nitrogen through the compressor or restrictor.
4. Always flush components in opposite direction of refrigerant flow.
5. Flush evaporator through the low pressure line with the high pressure line removed.
6. Blow through the refrigerant line from accumulator to compressor in flow direction of refrigerant (there is no thread on connection to compressor).
7. If any component has dark thick deposits that cannot be removed with compressed air, replace component.
8. Thin light gray deposits in refrigerant lines and hoses are normal and do not impair the function of the system.
9. Always replace accumulator and restrictor after flushing.

Flush refrigerant system with compressed air and nitrogen if

1. Refrigerant oil is dark and viscous (thick).
2. Too much refrigerant oil is in the system following compressor replacement.
3. Unclear or do not know how much refrigerant oil is in system.
4. Moisture, dirt or other impurities have entered the refrigerant system (i.e. following an accident).
5. Unable to pull a constant vacuum during evacuation of a leak-free system due to excessive moisture in the system.
6. Refrigerant system has been open longer than the time required for normal repairs (i.e. following an accident).
7. Based on temperature and pressure measurements, system is diagnosed with moisture contamination.
8. Compressor is replaced due to noises or internal damage.
9. Required after replacing certain components in certain situations, see A/C refrigerant system, components, replacing. See «A/C REFRIGERANT SYSTEM (R-134A), REPLACING COMPONENTS»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-replacing-components) .

Using VAG 1551 Scan Tool (ST), check DTC memory for any electrical, vacuum or air distribution malfunctions. See DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02) . Correct/repair as necessary before proceeding.

1. There are no shut off requirements for the compressor: Read measuring value block, display group 001, display field 1
2. The triggering and function of back pressure and recirculation door is OK.
3. All air ducts, seals and covers are OK.

If one of the following conditions exists, follow recommended service

A/C does not cool (cooling has stopped completely)

1. Check refrigerant system pressures. See «A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-checking-pressures) .

Insufficient cooling during all driving or engine speed (RPM)

1. Check refrigerant system pressures. See «A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-checking-pressures) . Low pressure switch -F73- shuts compressor off The high pressure switch -F118 shuts compressor off There is no outside air flow or air flow is severely restricted (evaporator iced up)

A/C compressor noisy

1. Tighten A/C compressor and compressor bracket mounting bolts using torque wrench.
2. Check routing of A/C refrigerant hoses and lines; hoses and lines must not contact other components and must be installed without binding, reposition or realign as necessary.

A/C compressor noisy immediately after switching A/C ON and/or when driving around corners or braking "refrigerant shock" -refrigerant system Overcharged

1. Discharge refrigerant system, evacuate and recharge.

With an otherwise properly operating A/C system, water sprays out of instrument panel vents

1. Check evaporator housing drain hose for proper routing (should not be kinked).
2. Check evaporator housing drain valve.

Note. Check both evaporator drain plugs for correct installation (should not be pinched or bent). Check both drain valves. Must not be plugged with wax, dirt or undercoating (clean if necessary). Valve flaps must close properly. Check air plenum cover (must be properly installed and not damaged).

A/C refrigerant system (R-134a), replacing components

1. The following replacement parts (compressor, accumulator, evaporator and compressor) were shipped charged with nitrogen gas. With time this charge drops, i.e. the pressure of the nitrogen charge is so small, that upon first opening gas may not escape.
2. All components of the refrigerant system which are being sent in for quality monitoring, should be closed (use original threaded assembly of replacement parts).

Note. Since in the replacement part process, parts can be stored for a longer period of time and at various locations, it could happen that upon first opening (even with parts of the same number) gas may or may not escape. Therefore remove sealing caps carefully on connectors of parts and allow nitrogen gas to release slowly.

1. Close all open connectors and lines (moisture penetration).
2. Replace restrictor.

For leaking or damaged components (except for compressor and accumulator), refrigerant circuit was completely empty (no charge)

1. Remove faulty component.
2. Remove compressor.
3. Remove oil drain plug from compressor. NOTE: Rotate compressor by hand to speed up oil draining process. The compressor oil drain plug O-ring has been replaced with a sealing ring, always replace.
4. Drain old refrigerant oil out of compressor into a measuring container. Record volume of refrigerant oil drained.
5. Subsequently, fill compressor with new refrigerant oil, the amount of oil equal to old refrigerant oil drained. NOTE: Fill amounts for refrigerant oil. See «A/C REFRIGERANT SYSTEM (R-134A), CAPACITIES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . To ensure adequate compressor lubrication, add at least 80 cm 3 (2.7 oz.) of refrigerant oil into compressor, the remainder can be added to new accumulator. See «A/C REFRIGERANT SYSTEM (R-134A), CAPACITIES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . If there is dirt in the compressor of an open refrigerant circuit (e.g. during an accident), replace compressor.
6. Blow through circuit with compressed air and nitrogen. See «A/C REFRIGERANT SYSTEM (R-134A), FLUSHING WITH COMPRESSED AIR AND NITROGEN»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-flushing-with) .
7. Replace accumulator and restrictor.
8. Assemble refrigerant circuit, evacuate and charge.

For leaky or damaged components (except for the compressor and accumulator) there is still refrigerant in the refrigerant circuit.

1. Discharge refrigerant circuit.
2. Remove faulty component, blow through with compressed air, collect all emitting oil in a measuring container. Refrigerant oil amount blown out of system, plus 20 cm 3 (0.7 oz.) in evaporator, plus 10 cm 3 (0.3 oz.) from condenser, refrigerant lines and hoses, is replaced as new refrigerant oil amount in the new component.
3. Replace restrictor.
4. Assemble refrigerant circuit, evacuate and charge.

Replace compressor, without it being necessary to blow through the refrigerant system with compressed air and nitrogen (e.g. exterior damage after an accident).

1. Discharge refrigerant circuit.
2. Remove damaged compressor.
3. Remove oil drain plug from compressor.
4. Drain old refrigerant oil out of faulty compressor into a measuring container. Record volume of drained refrigerant oil. NOTE: Rotate compressor by hand to speed up oil draining process. The O-ring on the compressor oil drain plug has been replaced with a sealing ring; always replace.
5. Drain refrigerant oil also out of replacement compressor into a clean container. Refill replacement compressor with the same amount of fresh oil which was poured out of faulty compressor.

Example

From the faulty compressor only 70 cm 3 (2.4 oz.) of refrigerant oil was poured out. From the replacement compressor 220 cm 3 of refrigerant oil poured out (a small amount remains in compressor). 70 cm 3 (2.4 oz.) of refrigerant oil needs to be poured back into replacement compressor (oil originally from replacement compressor, held in clean container).

Note. If a larger amount of refrigerant oil poured out of the faulty compressor, more than approx. 80 cm 3 (2.7 oz.) the remaining refrigerant oil can be used for the condenser or accumulator.

1. Replace restrictor.
2. Assemble refrigerant circuit, evacuate and recharge.

Replace compressor due to leaks or interior damage (e.g. noises or no power)

1. Discharge refrigerant circuit.
2. Remove compressor. NOTE: If there is interior damage (to compressor) check refrigerant hoses, if there are chips embedded, replace hose.
3. Blow through refrigerant circuit with compressed air and nitrogen. See «A/C REFRIGERANT SYSTEM (R-134A), FLUSHING WITH COMPRESSED AIR AND NITROGEN»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-flushing-with) .
4. Replace accumulator and restrictor.
5. Assemble refrigerant circuit, evacuate and charge.

Replace accumulator and restrictor after blowing through the refrigerant circuit e.g. caused by penetrating moisture (the refrigerant circuit was open over longer periods of time) or contamination (dirt)

1. Discharge refrigerant circuit.
2. Remove compressor.
3. Eliminate cause of malfunction.
4. Blow through refrigerant circuit with compressed air and nitrogen. See «A/C REFRIGERANT SYSTEM (R-134A), FLUSHING WITH COMPRESSED AIR AND NITROGEN»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning__ac-refrigerant-system-r-134a-flushing-with) .
5. Remove oil drain plug out of compressor.
6. Drain old refrigerant oil out of compressor into a measuring container. Record volume of refrigerant oil drained. NOTE: Rotate compressor by hand to speed up oil draining process. The compressor oil drain plug O-ring has been replaced with a sealing ring, always replace.
7. Then fill compressor with new refrigerant oil, the amount of oil must be equal to old refrigerant oil drained. NOTE: Fill amounts for refrigerant oil. See «A/C REFRIGERANT SYSTEM (R-134A), CAPACITIES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . To ensure adequate compressor lubrication, add at least 80 cm 3 (2.7 oz.) of refrigerant oil into compressor, the remainder can be added to new accumulator. See «A/C REFRIGERANT SYSTEM (R-134A), CAPACITIES»(/audi/a8/d2-1994-1999/remont/automatic-hvac-system/#air-conditioning) . NOTE: If there is dirt in the compressor of an open refrigerant circuit (for example, during an accident), replace compressor.
8. Blow through A/C circuit with compressed air and nitrogen.
9. Replace accumulator and restrictor.
10. Assemble refrigerant circuit, evacuate and charge.

Replace accumulator, without it being necessary to blow through refrigerant circuit with compressed air and nitrogen (e.g. damage caused by an accident), no refrigerant flowed out and no moisture and dirt have penetrated the circuit

1. Discharge refrigerant circuit.
2. Replace restrictor.
3. Remove accumulator.
4. Clean accumulator.
5. Weigh removed accumulator.
6. Fill new accumulator with new refrigerant oil until it weighs as much as the removed accumulator.
7. Install accumulator.
8. Assemble refrigerant circuit, evacuate and recharge.

See also:
• OUTPUT DIAGNOSTIC TEST MODE (DTM) (FUNCTION 03)
• BUMPER
• NOISE INSULATION PANEL, REMOVING AND INSTALLING
• MOUNTING BRACKET
• VAG 1551 (VAG 1552) SCAN TOOL (ST), CONNECTING AND SELECTING FUNCTIONS
• CODE CONTROL MODULE (FUNCTION 07)
• DIAGNOSTIC TROUBLE CODE (DTC) MEMORY, CHECKING (FUNCTION 02)
• READ MEASURING VALUE BLOCK (FUNCTION 08)
• DISPLAY GROUP 001 - A/C COMPRESSOR CUT-OFF CONDITIONS, VOLTAGE FOR A/C CLUTCH -N25-, VOLTAGE TO TERMINAL 15 AND REQUIREMENT FOR RECIRCULATING AIR MODE/SENSOR FOR AIR QUALITY -G238
• WIPER/WASHER SYSTEMS
• POWER BRAKE BOOSTER
• INSTRUMENT PANEL
• SYSTEM CHANGES FROM M.Y. 2000 (WITH REVISED DRIVER'S INFORMATION DISPLAY).
• RADIO, TELEPHONE, NAVIGATION, TRIP COMPUTER
• ADAPTATION (FUNCTION 10)
• BASIC SETTING (FUNCTION 04)
• LIGHTS, SWITCHES - EXTERIOR
• A/C REFRIGERANT SYSTEM (R-134A), SAFETY MEASURES
• A/C SYSTEM REFRIGERANT SYSTEM, SERVICING
• A/C REFRIGERANT SYSTEM (R-134A), DISCHARGING
• A/C REFRIGERANT SYSTEM (R-134A), PRESSURE & TEMPERATURE RELATIONSHIPS
• A/C REFRIGERANT R-134A, PROPERTIES
• A/C REFRIGERANT SYSTEM (R-134A), CHECKING PRESSURES
• A/C COMPRESSOR FROM MOUNTING BRACKET, REMOVING AND INSTALLING
• A/C PRESSURE SWITCH -F129-, FUNCTIONS
• O-rings
• REMOVING AND INSTALLING CLUTCH PLATE BOLT
• PULLING OFF CLUTCH DISC
• CHECKING AND ADJUSTING GAP
• INSTALLING MAGNETIC COIL
• A/C COMPRESSOR, REMOVING AND INSTALLING
• DUST AND POLLEN FILTERS, REMOVING AND INSTALLING
• PUMP VALVE UNIT, REMOVING AND INSTALLING
• PUMP VALVE UNIT, REPLACING
• AIR FLOW FLAP MOTOR -V71-, REMOVING AND INSTALLING
• A/C EVAPORATOR, REMOVING AND INSTALLING
• RECIRCULATION FLAP MOTOR -V113-, REMOVING AND INSTALLING
• CONTROL MODULE FOR FRESH AIR BLOWER -J126-, REMOVING AND INSTALLING
• A/C CONDENSER, REMOVING AND INSTALLING
• Sensor for air quality -G238-, function
• SENSOR FOR AIR QUALITY -G238-, REMOVING AND INSTALLING
• FLAP AND VENT MOTORS, SERVICING
• LEFT CENTER VENT MOTOR -V110- AND RIGHT CENTER VENT MOTOR -V111-, REMOVING AND INSTALLING
• CLIMATE CONTROL COMPONENTS IN PASSENGER COMPARTMENT, UPDATES FROM M.Y. 2000
• A/C CONTROL HEAD -E87-, REMOVING AND INSTALLING
• INSTRUMENT PANEL INTERIOR TEMPERATURE SENSOR -G56-, REMOVING AND INSTALLING
• SIDE WINDOW AIR OUTLET IN RIGHT (LEFT) OF INSTRUMENT PANEL, REMOVING AND INSTALLING
• CENTER AIR OUTLET IN INSTRUMENT PANEL, REMOVING AND INSTALLING
• TEMPERATURE REGULATOR FLAP MOTOR -V68- AND RIGHT FOOTWELL FLAP MOTOR -V109-, REMOVING AND INSTALLING
• PASSENGER-SIDE HEATER CORE, REMOVING AND INSTALLING
• DEFROSTER FLAP MOTOR -V107-, REMOVING AND INSTALLING
• LEFT FOOTWELL FLAP MOTOR -V108- AND REAR FOOTWELL VENT MOTOR -V112-, REMOVING AND INSTALLING
• CENTER VENT ADJUSTING MOTOR -V102-, REMOVING AND INSTALLING
• DRIVER-SIDE HEATER CORE, REMOVING AND INSTALLING
• Changes to model year 2000 vehicles
• VERSION "1" HEATER CORE, INSTALLING
• VERSION "2" HEATER CORE, INSTALLING
• AUTOMATIC CLIMATE CONTROL COMPONENTS IN PASSENGER COMPARTMENT, SERVICING
• AUTOMATIC CLIMATE CONTROL COMPONENTS IN ENGINE COMPARTMENT, SERVICING
• AUTOMATIC CLIMATE CONTROL SYSTEM HEATING PERFORMANCE AND OPERATION OF PUMP VALVE UNIT, TESTING
• A/C REFRIGERANT LINES FROM NIPPONDENSO COMPRESSOR, REMOVING AND INSTALLING
• RESTRICTOR, REMOVING AND INSTALLING
• A/C REFRIGERANT SYSTEM (R-134A), REPLACING COMPONENTS
• A/C REFRIGERANT SYSTEM (R-134A), COMPONENTS
• HEATER CORES, REMOVING AND INSTALLING
• AIR CONDITIONER HOUSING, REMOVING AND INSTALLING
• DISASSEMBLING AND ASSEMBLING INTAKE SHAFT
• AIR CONDITIONER HOUSING (LOWER) AND AIR DISTRIBUTION HOUSING, DISASSEMBLING AND ASSEMBLING
• AIR DISTRIBUTION HOUSING, DISASSEMBLING AND ASSEMBLING
• DISASSEMBLING AND ASSEMBLING COVER WITH RECIRCULATING AIR FLAP
• HIGH PRESSURE SERVICE CONNECTION WITH SCHRADER VALVE
• A/C REFRIGERANT SYSTEM (R-134A), FLUSHING WITH COMPRESSED AIR AND NITROGEN