Refrigerant R134A - Servicing: Other Audi S8 D3 facelift

Laws and Regulations

> Converting R12 Refrigerant Circuit to R134a Refrigerant Circuit and Servicing

> Keeping Refrigerant Records

Note. The laws and regulations listed below are applicable in Germany. Different or additional laws and regulations may apply in other countries.

8 Operation, maintenance, shutdown, obligation to accept return

(1) With regard to operation, repair and shutdown of items containing refrigerants as defined in 3, it is prohibited to contravene the state of the art by allowing the substances they contain to escape into the atmosphere.

A record must be kept of the quantities used during operation and maintenance and presented to the relevant authorities on request.

(2) Distributors of the substances and preparations listed in 1 Para. 1 and 2 are obliged to accept the return of such substances and preparations after use or to appoint a third party to accept return of these.

(3) The maintenance and shutdown of items containing refrigerants as defined in 3, as well as acceptance of return of the substances and preparations listed in 1 Para. 1 and 2 may only be undertaken by persons with the necessary expert knowledge and technical equipment.

9 Criminal offences and infringements of the law

(3) An infringement of the law in terms of 26 Para. 1 No. 7 of the Law on Chemicals is constituted by wilful or negligent contravention of 8 Para. 1 Clause 1 during operation, maintenance or shutdown of items containing refrigerants as defined in 3 by allowing substances contained in these to escape into the atmosphere contrary to the state of the art, or by wilful or negligent contravention of the obligation to keep records as defined by 8 Para. 1 Clause 2.

TRG (technical regulations for compressed gases) 400, 401, 402

Only excerpts concerning vehicle manufacturers and workshops are listed below.

TRG 400 (general regulations for charging systems)

2. Definition of terms and explanatory notes

2.1 Charging systems

2.1.1 Charging systems are systems for filling mobile compressed-gas vessels. The charging system includes the premises and facilities concerned.

2.4 Charging systems requiring a permit

Charging systems requiring a permit are ones used to transfer compressed gases to mobile compressed-gas vessels for supplying to third parties.

2.5 Charging systems not requiring a permit are ones used for transferring compressed gases to mobile compressed-gas vessels for internal use only.

TRG 401 (installation of charging systems)

Does not apply to vehicle manufacturers or workshops.

TRG 402 (operation of charging systems)

2. Employees and employee instruction

2.1 Charging systems are only to be operated and maintained by personnel

1. Aged 18 and above
2. Possessing the necessary technical knowledge
3. Who can be relied on to work diligently

2.2 Supervised work may also be performed by personnel not satisfying the requirements stipulated in item 2.1, points 1 and 2.

2.3 Employees are to be given instruction on the following topics before beginning work and at regular, appropriate intervals, however at least once a year

1. Hazards specifically associated with handling compressed gases
2. Safety regulations, particularly the applicable TRG
3. Procedures in the event of malfunction, damage and accidents
4. The use of fire-extinguishing and protective equipment

1. Operation and maintenance of the charging system on the basis of the instructions for use

Charging (a separate TRG applies to vessels from other countries and their charging)

A compressed-gas vessel is only to be filled with the compressed gas declared on it and the quantity must comply with the stipulated pressure, weight or volume data (refer to g15, Para. 2, pressure vessel regulations).

2. In the case of vessels approved for use with several types of compressed gas, the compressed gas with which it is to be filled and - if the compressed gas has a tc not = -10°C (tc = critical temperature) - the maximum permissible charging weight in line with TRG 104 No. 3.3 must be marked on the vessel prior to connection for filling.

3. Compressed-gas vessels marked with the maximum permissible charge pressure in bar at 15°C must be filled manometrically. If, at the time of filling, the temperature is not 15°C, the pressure corresponding to the prevailing temperature must be established; it must be ensured that the permissible charge pressure at 15°C is not exceeded in the compressed-gas vessel. The charged vessels are to be checked by way of random pressure measurements to determine possible overfilling.

4. Compressed-gas vessels on which the maximum permissible capacity is indicated by the net weight (filling weight, permissible weight of fill) in kilograms must be filled gravimetrically. The vessels are to be weighed during filling and subsequently subjected to a weight check on special scales to establish possible overfilling. Scales used for this purpose must be calibrated.

5. Under certain conditions, gases with a tc not = +70°C may be transferred volumetrically from compressed-gas vessels with a maximum volume of 150 l to compressed-gas vessels with a volume of max. 1000 ccm. The stipulations of the TRG apply to the transfer of liquefied gas to cylinders used by workmen.

6. Vessels in vehicles for

(1) Gases with tc not = +70°C (refer to TRG 101 Annex 3)

(2) Industrial gas mixtures with tc not = +70°C (refer to TRG 102 Annex 1 Groups 3)

(3) Liquefied extremely low-temperature compressed gases (refer to TRG 103) may, contrary to item 4, be filled volumetrically if the charging system and/or the vessels is/are equipped with devices for measuring or limiting the volume of the charge and with the exception of motor vehicle vessels as per item 3 for measuring the temperature of the charge. When filling volumetrically, it must be ensured that the permissible charge weight indicated on the vessel is not exceeded. To determine possible overfilling, the filled containers are to be checked gravimetrically on a calibrated scale or provided that the pressurized gases are not highly toxic volumetrically. Volumetric checking requires the use of appropriate equipment with completely separate charging and checking devices.

7. Charging and check measurements are to be performed by different people. Check measurements must be performed immediately upon completion of the filling process.

8. Overfilled vessels must be drained immediately and in a safe manner until the permissible fill is attained. The compressed-gas fill is then to be determined again.

9. Items 4 to 7 do not apply to vessels for liquefied, extremely low-temperature compressed gases which are neither flammable nor toxic; this does not affect the provisions of road traffic legislation.

10. When filling compressed gas vessels with liquefied gases at charging temperatures not = -20°C, the compressed gas vessel (if the vessel material has not been tested for temperatures not = -20 C) is not to be released from the charging system for transportation until the vessel wall temperature is not = +20°C.

Recycling and refuse law

Legislation on the handling and disposal of refrigerants and refrigerant oils is contained in the BIMISCH (German Immission Protection Law) and the Recycling and Refuse law --> Audi-ServiceNet, Handbooks, HSO Environment 2 and 3.

Disposal of refrigerant

Refrigerants intended for disposal are to be transferred to marked recycling containers, observing the permissible filling quantity.

Disposal of refrigerant oil

Used refrigerant oils from systems employing halogenated hydrocarbons are to be disposed of as waste subject to special supervision. They are not to be mixed with other oils or substances. Proper storage and disposal must be ensured in line with local regulations.

German technical, work safety and accident prevention regulations can be obtained from (addresses in other countries can be obtained from the relevant authorities)

BeuthVerlag GmbH

Burggrafenstr. 6

10787 Berlin

Carl Heymanns Verlag KG

Luxemburger Str. 449

50674 Koln

Converting R12 Refrigerant Circuit to R134a Refrigerant Circuit and Servicing

Note. For environmental reasons and on account of the corresponding legislation, refrigerant R12 can no longer be manufactured or supplied. Refrigerant R134a has been developed as a replacement for R12. Air conditioning systems developed and designed for refrigerant R12 cannot however simply be charged with refrigerant R134a. To ensure trouble-free operation of the air conditioning system even after conversion, various components of the refrigerant circuit must be replaced.

Keeping Refrigerant Records

The environmental statistics law requires records to be kept on the use of refrigerants.

Air Conditioning System Principles

Physical Principles

Scheme 5

The four known states of water also apply to air conditioning system refrigerants.

1. Gas (invisible)
2. Vapor
3. Liquid
4. Solid

Scheme 6

When water is heated in a vessel (heat absorption), water vapor can be seen to rise. If the vapor is further heated through heat absorption, the visible vapor turns into invisible gas. The process is reversible. If heat is extracted from water in gaseous form - A - , it changes first to vapor - B - , then to water and finally to ice.

A - Heat absorption

B - Heat emission

Heat Flow

Any substance consists of a mass of moving molecules. The fast moving molecules of a warmer substance give off some of their energy to the cooler and thus slower molecules. As a result, the molecular motion of the warmer substance slows down and that of the colder substance is accelerated. Heat always flows from a warmer to a colder substance. This process continues until the molecules of both substances are moving at the same speed. They are then at the same temperature and no further heat exchange takes place.

Pressure and Boiling Point

The boiling point given in tables for a liquid is always referenced to an atmospheric pressure of 1 bar. If the pressure acting on a fluid changes, its boiling point also changes.

Note. Pressure is measured in different units: 1 MPa (mega pascal) corresponds to 10 bar positive pressure or 145 psi, 1 bar absolute pressure corresponds to 0 bar positive pressure and thus to the ambient pressure (atmospheric pressure).

For example, water boils at a lower temperature the lower the pressure.

The vapor pressure curves for water and refrigerant R134a show for example that, at constant pressure, reducing the temperature changes vapor to liquid (in condenser) or that, for instance, reducing pressure causes the refrigerant to change from liquid to vapor state (evaporator).

Vapor pressure curve for water

Scheme 7

A - Liquid

B - Gas

C - Vapor pressure curve for water

1 - Pressure acting on liquid in bar (absolute)

2 - Temperature in C

Vapor pressure curve for refrigerant R134a

Scheme 8

A - Liquid

B - Gas

D - Vapor pressure curve for refrigerant R134a

1 - Pressure acting on liquid in bar (absolute)

2 - Temperature in C

Refrigerant R134a Vapor Pressure Table

The vapor pressure table for every refrigerant is published in literature for refrigeration system engineers. This table makes it possible to determine the vapor pressure acting on the column of liquid in a vessel if the temperature of the vessel is known.

As there is a characteristic vapor pressure table for every refrigerant, refrigerant can be identified by measuring pressure and temperature.

Note. At absolute pressure, "0 bar" corresponds to an absolute vacuum. Normal atmospheric pressure corresponds to "1 bar" absolute. On the scales of most pressure gauges, "0 bar" corresponds to an absolute pressure of 1 bar (can be seen from "-1 bar" mark below "0"). Pressure is measured in different units: 1 MPa (mega pascal) corresponds to 10 bar positive pressure or 145 psi, 1 bar absolute pressure corresponds to 0 bar positive pressure and thus to the ambient pressure (atmospheric pressure).

Vehicle air conditioning systems make use of the vaporization and condensation process. Use is made of a substance with a low boiling point.

The refrigerant employed is tetrafluoroethane R134a, which boils at -26.5 C at a vapor pressure of "1 bar".

Physical Data

Critical Point

The critical point (critical temperature and critical pressure) is that above which there is no longer a boundary between liquid and gas.

A substance above its critical point is always in the gaseous state.

At temperatures below the critical point, all types of refrigerant in pressure vessels exhibit both a liquid and a gas phase, i.e. there is a layer of gas above the liquid.

As long as both liquid and gas are present in the vessel, the pressure is governed by ambient temperature. Refer to --> Air Conditioning System Principles .

Note. Different types of refrigerant are never to be mixed. Exclusive use is to be made of the refrigerant specified for the respective air conditioning system.

Environmental Aspects

1. R134a is a fluorocarbon and contains no chlorine.
2. R134a has a shorter atmospheric life span than refrigerant R12.
3. R134a does not deplete the ozone layer.
4. The global warming effect of R134a is "ten" times less than that of refrigerant R12.

Trade Names and Designations

The refrigerant R134a is currently available under the following trade names

1. H-FKW 134a
2. SUVA 134a
3. KLEA 134a

Note. Different trade names may be used in other countries. Of the wide range of refrigerants available, this is the only one which may be used for vehicles. The designations Frigen and Freon are trade names. They also apply to refrigerants which are not to be used in vehicles.

Color

Like water, refrigerants are colorless in both vapor and liquid form. Gas is invisible. Only the boundary layer between gas and liquid is visible (liquid level in tube of charging cylinder or bubbles in inspection port). Liquid refrigerant R134a may have a colored (milky) appearance in an inspection port. This cloudiness is caused by partially dissolved refrigerant oil and does not indicate a fault.

Vapor Pressure

In a partially filled, closed vessel, the quantity of refrigerant evaporating from the surface equals the quantity returning to the liquid state as vapor particles condense. This state of equilibrium occurs under the influence of pressure and is often called vapor pressure. Vapor pressure is a function of temperature. Refer to --> Air Conditioning System Principles .

Physical Properties

As the vapor pressure curves of R134a and other refrigerants are sometimes very similar, unequivocal identification cannot be made simply on the basis of pressure.

When using R134a, the compressor is lubricated by means of special synthetic refrigerant oils, e.g. PAG oils (polyalkylene glycol oils).

Reaction with Metals

In its pure state, refrigerant R134a is chemically stable and does not corrode iron or aluminum.

Refrigerant impurities such as chlorine compounds however cause corrosion of certain metals and plastics. This can lead to blockage, leaks or deposits on the compressor piston.

Critical Temperature/Critical Pressure

The refrigerant R134a remains chemically stable up to a gas pressure of 39.5 bar (corresponding to a temperature of 101 C). Above this temperature, the refrigerant decomposes (refer to Combustibility ).

Water Content

Only very small amounts of water are soluble in liquid refrigerant. On the other hand, refrigerant vapor and water vapor mix in any ratio.

Any water in the refrigerant circuit will be entrained in droplet form once the dryer in the receiver or reservoir has absorbed as little as approx. 7 g of water. This water flows as far as the nozzle of the expansion valve or restrictor and turns to ice, the A/C system no longer has a cooling effect.

Water destroys the air conditioner as it combines with other impurities at high pressures and temperatures to form acids.

Combustibility

Refrigerant is non-flammable. In fact, it has a fire-retardant or extinguishing effect. Refrigerant decomposes when exposed to flames or red-hot surfaces. UV light (occurring for example during electric welding) also causes refrigerant decomposition. The resultant decomposition products are toxic and are not to be inhaled. However, irritation of the mucous membranes provides an adequate and timely warning.

Charge Factor

A vessel must have space for vapor as well as liquid. As the temperature rises, the liquid expands. The vapor-filled space becomes smaller. At a certain point, there will only be liquid in the vessel. Beyond this, even a slight increase in temperature causes great pressure to build up in the vessel as the liquid attempts to continue expanding despite the absence of the necessary space. The resultant forces are sufficient to rupture the vessel. To avoid overfilling of vessels, regulations governing compressed gases specify the number of kilograms of refrigerant with which a vessel may be filled per liter of internal vessel volume. The product of multiplying this "charge factor" by the internal volume of the vessel is the permissible capacity. The figure for refrigerant used in vehicles is 1.15 kg/liter.

Leaks, Detecting

External damage, for example, can cause a leak in the refrigerant circuit. The small quantity of refrigerant escaping from minor leaks can be detected for example using an electronic leak detector or by introducing a leak detection additive into the refrigerant circuit. Electronic leak detectors are capable of registering leaks with refrigerant losses of less than 5 g per year.

Note. Use must be made of leak detectors designed for the composition of the respective refrigerant. For example, a leak detector for R12 refrigerant is not appropriate for R134a, as R134a refrigerant has no chlorine atoms and the leak detector does not therefore respond.

Refrigerant Oil

Refrigerant oil mixes with the refrigerant (about 20-40%, depending on compressor type and amount of refrigerant) and circulates constantly in the system, lubricating the moving parts.

Special synthetic refrigerant oils, e.g. polyalkylene glycol (PAG) oil, are used in conjunction with R134a air conditioning systems. This is necessary as mineral oil, for example, does not mix with R134a. In addition, the materials of the R134a air conditioning system could be corroded as a result of mixture flowing through the refrigerant circuit under pressure at high temperatures or breakdown of the lubricating film in the compressor. The use of non-approved oils can lead to the failure of the air conditioning system and exclusive use is therefore to be made of authorized oils.

Type of oil for R134a in motor vehicles: PAG

Note. Do not store refrigerant oils in open containers as they are extremely hygroscopic (water-absorbing). Always keep oil containers sealed. Do not re-use old refrigerant oil. Dispose of as used oil of unknown origin . Ester-based oils are only intended for use with large systems (not for motor vehicle air conditioners).

Properties

The most important properties are a high degree of solubility with refrigerant, good lubricity, absence of acid and minimal water content. It is therefore only permissible to use certain specified oils. For list of approved refrigerant oils and capacities, refer to --> Approved Refrigerant Oils .

PAG oils, which are appropriate for refrigerant R134a, are highly hygroscopic and do not mix with other oils. Opened containers should therefore be closed again immediately to prevent ingress of moisture. Moisture and acids promote ageing of refrigerant oil, causing it to become dark and viscous as well as corrosive towards metals.

Note. On account of its chemical properties, refrigerant oil is not to be disposed of together with engine or gear oil . Only oil approved for the compressor may be used for refrigerant circuits containing refrigerant R134a --> Approved Refrigerant Oils .

Comfort

A basic requirement for concentration and safe driving is a feeling of comfort in the passenger compartment. Especially when it is hot and humid, comfort can only be attained through the use of air conditioning. Comfort can of course also be enhanced by opening windows/sun roof or increasing the air output. Such a course of action is however associated with certain drawbacks for the occupants of the vehicle, e.g. more noise, droughts, exhaust fumes and unfiltered pollen (unpleasant for allergy sufferers).

Climate control together with a good heating and ventilation system concept can create a sense of well-being and comfort by regulating temperature, humidity and air circulation in the passenger compartment to suit ambient conditions, with the vehicle both stationary and moving.

Other important advantages of air conditioning

1. Purification of the air supplied to the passenger compartment (dust and pollen, for example, are washed out by the moist fins of the evaporator and removed with the condensate).
2. Pleasant temperature levels (example: Mid-size car after short travelling time, ambient temperature 30 C in the shade and vehicle exposed to sunlight)

Environmental Aspects

Since roughly 1992, the air conditioning systems of newly manufactured cars have been successively converted to refrigerant R134a. This refrigerant contains no chlorine and therefore does not deplete the ozone layer.

Until roughly 1992, refrigerant R12 was used for air conditioning systems. Due to its chlorine atoms, this CFC has a high potential for depleting the ozone layer as well as a tendency to increase the greenhouse effect.

For environmental protection reasons, refrigerants must not be released into the atmosphere --> Laws and Regulations (laws and regulations).

General Work Safety

1. As per VBG 20, German industrial liability insurance association (other regulations may apply in other countries)

Product Properties

Refrigerants used in motor vehicle air conditioning systems belong to the new generation of refrigerants based on chlorine-free, partially fluorinated hydrocarbons (H-FKW, R134a; other names may be used in other countries).

With regard to their physical properties, these are refrigerants which have been liquefied under pressure. They are subject to the regulations governing pressure vessels and use is only to be made of approved and appropriately marked containers.

Compliance with specific conditions is required to ensure safe and proper use.

Refrigerant, Handling

If refrigerant vessels are opened, the contents may escape in liquid or vapor form. The higher the pressure in the vessel, the more vigorous the process.

The pressure level is governed by two factors

1. The type of refrigerant in the vessel. "Rule: The lower the boiling point, the higher the pressure"
2. The temperature level. "Rule: The higher the temperature, the higher the pressure"

Wear safety goggles

Put on safety goggles to prevent refrigerant getting into the eyes, as this could cause severe injury from exposure to cold.

Wear protective gloves and apron

Greases and oils dissolve readily in refrigerants. They would therefore destroy the protective layer of grease if allowed to come into contact with the skin. Degreased skin is however sensitive to the cold and germs.

Do not allow liquid refrigerant to come into contact with the skin

The refrigerant draws heat for evaporation from the surrounding area - even if this is the skin. This may give rise to extremely low temperatures and result in local frostbite (boiling point of R134a: -26.5 C at ambient pressure).

Do not inhale refrigerant vapors

If highly concentrated refrigerant vapor escapes, it mixes with the surrounding air and displaces the oxygen necessary for breathing.

Smoking is absolutely prohibited

A burning cigarette can cause refrigerant to decompose. The resultant substances are toxic and must not be inhaled.

Welding and soldering on refrigeration systems

Before performing welding or soldering work on vehicles in the vicinity of air conditioning system components, extract refrigerant and remove remnants by blowing out with nitrogen.

The products of refrigerant decomposition due to the effect of heat are not only toxic, but may also have a highly corrosive effect on pipes and system components. They mainly take the form of hydrogen fluoride.

Pungent odor

A pungent odor indicates that the products of decomposition mentioned above have already formed. Avoid inhaling these substances under all circumstances, as otherwise the respiratory system, lungs and other organs could be damaged.

First aid

1. Following contact with eyes or mucous membranes, immediately rinse with copious amounts of running water and consult an eye specialist.
2. Following contact with the skin, immediately remove clothing affected and rinse skin with copious amounts of water.
3. Following inhalation of highly concentrated refrigerant vapors, person concerned is to be taken immediately into the open air. Call a doctor. Administer oxygen in the event of breathing difficulties. If the person affected is having great difficulty breathing or is not breathing at all, tilt back head and administer artificial respiration.

Pressure Vessels, Handling

1. Secure vessels to prevent them falling over.

Secure upright cylinders to stop them falling over and cylinders lying flat to stop them rolling away.

1. Vessels are never to be thrown.

If dropped, the vessels could be so severely deformed that they rupture. The refrigerant evaporates immediately, liberating considerable force. Flying fragments of cylinders can cause severe injuries.

Valves may break off if cylinders are not properly transported. To protect the valves, cylinders are only to be transported with protective cap screwed on.

1. Never store in the vicinity of radiators.

High temperatures may occur in such areas. High temperatures are also accompanied by high pressures and the maximum permissible vessel pressure may be exceeded.

Do not heat in excess of 50 C

To avoid possible risk, pressure vessel regulations specify that vessels are not to be heated to in excess of 50 C.

Do not heat in an uncontrolled manner

Do not heat with a naked flame under any circumstances. Localized overheating can cause structural changes in the vessel material, which then reduce its ability to withstand pressure. There is also a danger of refrigerant decomposition due to localized overheating.

Seal empty vessels

Empty refrigerant vessels must always be sealed to prevent the ingress of moisture. Moisture causes corrosion of steel vessels. This weakens the vessel walls. In addition, rust particles penetrating into refrigeration systems from vessels will cause malfunctioning.

Safety Regulations for Working with Extraction and Charging Systems

1. Make sure the shut-off valves are closed before connecting the charging system to the air conditioning system.
2. Before disconnecting the charging system from the air conditioning system, make sure the charging process has been completed to stop refrigerant escaping into the atmosphere.
3. Once the purified refrigerant from the charging system has been transferred to an external compressed-gas cylinder, close the hand shut-off valves at the cylinder and charging system.
4. Do not expose charging system to moisture or use it in a wet environment.

1. Disconnect from power supply before performing service work on the charging system.
2. Never use an extension cable on account of the fire hazard. If the use of an extension cable is unavoidable, the minimum cross-section should be 2.5 mm 2 .
3. In case of fire, remove external cylinder.
4. Entrained oil from the air conditioning system drawn by the suction unit into the measurement vessel supplied is subsequently to be transferred to a sealed container, as it contains a small quantity of refrigerant which must not be released into the environment.

1. Following shutdown, A/C service station is to be secured to stop it rolling away.

R134a Safety Precautions

1. Welding, brazing and soldering work must not be performed on components of air conditioning system when charged. This also applies to vehicle welding and soldering work if there is a danger of air conditioner components becoming hot. When performing paintwork repairs, the temperature in the drying booth or preheating zone must not exceed 80 C.

Reason

Exposure to heat gives rise to considerable pressure in the system, which could cause the pressure relief valve to open.

Corrective action

1. Discharge refrigerant circuit using A/C service station.

Note. Damaged or leaking components of the air conditioning system are not to be repaired by welding or soldering. They must always be replaced.

Refrigerant vessels (e.g. charging cylinders of A/C service station) must never be subjected to excessive heat or exposed to direct sunlight.

Corrective action

1. Vessels must never be completely filled with liquid refrigerant. Without sufficient room for expansion (gas cushion), vessels will rupture with devastating effect in the event of an increase in temperature --> «Refrigerant R134a Properties»(ref-289226-S06178488182008062700000) .

Refrigerant is never to be transferred to systems or vessels in which air is present.

Corrective action

1. Evacuate systems and vessels before charging with refrigerant.

Basic Rules for Working on Refrigerant Circuit

General

1. Ensure absolute cleanliness when working.
2. Wear safety goggles and gloves when working with refrigerant and nitrogen.
3. Workshop extraction systems are to be switched on.

1. Use A/C service station to discharge refrigerant circuit, then unfasten screw connections and replace malfunctioning components.
2. Use caps to seal off opened assemblies and hoses to prevent ingress of moisture and dirt.
3. Make exclusive use of tools and materials intended for refrigerant R134a.
4. Re-seal opened refrigerant oil vessels to guard against moisture.

Note. After completing service work, screw sealing caps (with seals) onto all connections with valves as well as service connections. Before starting up air conditioning system, pay attention to vehicle-specific capacities --> Refrigerant R134a/Refrigerant Oil Capacities and Specifications . Do not top up refrigerant. Extract existing refrigerant and recharge system.

Refrigerant Circuit, Cleaning

Flush refrigerant circuit with refrigerant R 134a --> Refrigerant Circuit, Flushing with Refrigerant R134a (or with compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ) if

1. Moisture or dirt has entered into refrigerant circuit (e.g. following an accident)
2. Refrigerant oil is dark and viscous.
3. There is too much refrigerant oil in the refrigerant circuit after compressor replacement.
4. The A/C compressor had to be replaced on account of "internal" damage (e.g. noise or no output).

Note. When flushing components with compressed air and nitrogen, always extract the gas mixture escaping from the components using suitable extraction units (workshop extraction system).

Additional Notes for Vehicles with A/C Compressor Regulator Valve N280)

1. The engine is only to be started following complete assembly of the refrigerant circuit (constant compressor operation).
2. If engine has to be operated with the refrigerant circuit empty, only do so for as long as absolutely essential and avoid high engine speeds.

O-Rings

1. Use only seals which are resistant to refrigerant R134a and the related refrigerant oils. Color coding of O-rings is no longer employed. Black and colored O-rings are used.
2. Pay attention to correct ID of seals used .
3. Seals are only to be used once.
4. Before installing, moisten seals slightly with refrigerant oil (PAG oil).

Before starting up Air Conditioning System after Charging

1. Rotate compressor roughly 10 times by hand using the clutch plate or pulley of the A/C clutch.
2. Start engine with air conditioning system switched off (A/C Clutch N25 and A/C Compressor Regulator Valve N280 are not actuated).
3. Following engine idling speed stabilization, switch on compressor and run it for at least 10 minutes at idling speed with maximum cooling output.

Refrigerant Circuit and Components

> Components

> Refrigerant Circuit Design

> Refrigerant Circuit Quick-Release Connections

> Refrigerant Circuit Switches, Sensors, and Related Connections

> Refrigerant Circuit Pressures and Temperatures

> Refrigerant Circuit with Expansion Valve

> Refrigerant Circuit with Restrictor and Reservoir

> Using Pressure Gauge

> Service and Recycling Units

> Refrigerant Circuit Repair Information

1. All components of the refrigerant circuit submitted for quality observation are always to be sealed (use original sealing caps of replacement part).
2. Replace damaged or leaking components of refrigerant circuit --> «Refrigerant Circuit Components, Replacing»(ref-289226-S05629535382008062700000) .

Note. To date, the following replacement parts (compressor, reservoir, evaporator and condenser) have been filled with nitrogen gas. This charge is being gradually discontinued. Little or no pressure equalization is therefore noticeable on unscrewing sealing plugs from replacement parts.

Refrigerant Circuit Components, Arrangement and Influence on High and Low Pressure Sides

High pressure side: Condenser, receiver and restrictor or expansion valve to separate the high and low pressure liquid ends

High pressure results from the restrictor or expansion valve forming a constriction and causing the refrigerant to accumulate, thus leading to an increase in pressure and temperature.

Excess pressure occurs if too much refrigerant or refrigerant oil is used, the condenser is contaminated, the coolant fan is malfunctioning, the system is blocked or in the event of moisture in the refrigerant circuit (icing-up of restrictor or expansion valve).

Low pressure side: Evaporator, evaporator temperature sensor and compressor to separate high and low pressure gas ends

A drop in system pressure can be caused by loss of refrigerant, the restrictor or expansion valve (blockage), a malfunctioning compressor or an iced-up evaporator.

Scheme 9

The compressor is driven via a poly V-belt by the vehicle engine.

Compressor with A/C clutch

An electromagnetic coupling attached to the compressor provides the power link between pulley and compressor crankshaft when the air conditioning is switched on.

Compressor with no A/C clutch

An overload safeguard attached to the pulley of the compressor is tripped if the compressor does not move freely, thus protecting the belt drive against overload.

The compressor draws in refrigerant gas from the evaporator, compresses it and conveys it to the condenser.

Note. The compressor contains refrigerant oil which mixes with refrigerant R134a at all temperatures. The rating plate indicates the refrigerant for which the compressor is designed. A valve regulates the pressure on the low-pressure side within the specified range (control characteristic). On compressors with no A/C clutch, a regulator valve is externally actuated. On compressors with no A/C clutch, the engine is only to be started following complete assembly of the refrigerant circuit. To prevent compressor damage if the refrigerant circuit is empty, the A/C clutch is deactivated and the A/C Compressor Regulator Valve N280 no longer actuated (compressor idles with engine). If the refrigerant circuit is empty, a compressor with no A/C Clutch N25 (with A/C Compressor Regulator Valve N280) is switched to internal lubrication by way of a valve.

Scheme 10

The condenser dissipates heat from the compressed refrigerant gas to the surrounding air.

In this process, the refrigerant gas condenses to form liquid.

Evaporator

Scheme 11

The liquid refrigerant evaporates in the coiled pipes of the evaporator. The heat required for this is extracted from the air flowing past the evaporator fins. The air cools down. The refrigerant evaporates and is drawn in by the compressor together with the absorbed heat.

A defined quantity of refrigerant is supplied to the evaporator by way of a restrictor or expansion valve. In systems with an expansion valve the flow rate is regulated such that only gaseous refrigerant emerges at the evaporator outlet.

Scheme 12

To ensure that the compressor draws in only gaseous refrigerant, the reservoir collects the mixture of vapor and gas coming from the evaporator. The vapor becomes gaseous refrigerant.

An oil extraction hole ensures that refrigerant oil entrained in the circuit does not remain in the reservoir.

Any moisture penetrating into the refrigerant circuit during assembly is trapped by a filter (desiccant bag) in the reservoir.

Gaseous refrigerant with oil is drawn in by the compressor.

Note. Replace reservoir if refrigerant circuit has been open for a lengthy period and moisture has penetrated or if replacement is stipulated on the basis of a specific complaint --> Refrigerant Circuit Components, Replacing . Do not remove sealing plugs - A - and - B - until immediately prior to installation. If a reservoir is not sealed, the desiccant bag soon becomes saturated with moisture and can no longer be used. On installation, note arrow indicating direction of flow if applicable.

Scheme 13

The restrictor forms a constriction. This constriction restricts the flow, thus separating the refrigerant circuit into high and low pressure sides. Upstream of the restrictor, the refrigerant is warm due to the high pressure. Downstream of the restrictor, the refrigerant is cold due to the low pressure. A strainer is provided upstream of the constriction to trap dirt. The strainer downstream of the constriction is designed to atomize the refrigerant before it enters the evaporator.

Note. Arrow - A - on restrictor faces evaporator. Always replace after opening circuit. Different versions, observe notes in various customer service information sources --> Heating, air conditioning or --> Air conditioning .

Scheme 14

The receiver collects the droplets of liquid and conveys them in a continuous stream to the expansion valve. Any moisture penetrating into the refrigerant circuit during assembly is collected by a dryer in the receiver.

Note. Replace receiver if refrigerant circuit has been open for a lengthy period and moisture has penetrated or if replacement is stipulated on the basis of a specific complaint --> Refrigerant Circuit Components, Replacing . Only remove sealing plugs immediately prior to installation. If a receiver is not sealed, the desiccant bag soon becomes saturated with moisture and can no longer be used. On installation, note arrow indicating direction of flow if applicable. Depending on the construction of the refrigerant circuit, the receiver may also be secured on the condenser or installed in the condenser --> 87 - AIR CONDITIONING Depending on the construction of the refrigerant circuit, the desiccant bag as the dryer cartridge may also be installed in the condenser. --> 87 - AIR CONDITIONING

Scheme 15

The expansion valve atomizes the refrigerant flowing in and controls the flow rate in line with the quantity of heat transferred such that gas does not form until it reaches the evaporator outlet.

Note. Pay attention to correct part number when replacing expansion valve. Different characteristic curves matched to the appropriate circuit with Internally Regulated Compressor --> Pressure Checking, Vehicles with Restrictor, Reservoir and A/C Compressor Regulator Valve with Externally Regulated Compressor with Externally Regulated Compressor --> Pressure Checking, Vehicles with Expansion Valve, Receiver, and A/C Compressor Regulator Valve with Externally Regulated Compressor .

Scheme 16

These rings seal the joints between the individual components of the refrigerant circuit.

Only O-rings resistant to R134a refrigerant and the related refrigerant oils are to be used. This is guaranteed by genuine replacement parts.

O-rings

1. Always use only once.
2. Make sure diameters - a - and - b - are correct.
3. Moisten with refrigerant oil before installing --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)

Note. The color coding of O-rings for R134a refrigerant circuits has been discontinued. Use is made of black and colored seals --> 87 - AIR CONDITIONING .

Refrigerant Circuit Pipes and Hoses

The mixture of refrigerant oil and refrigerant R134a corrodes certain metals (e.g. copper) and alloys and dissolves certain hose materials. Genuine replacement parts are therefore always to be used.

The pipes and hoses are linked by threaded joints or special connectors.

Note. Observe specified torques for threaded joints and use the specified release tools for connectors.

Scheme 17

The pressure relief valve is attached to the compressor or receiver.

The valve opens at a pressure of approx. 38 bar and closes again once the pressure has dropped (approx. 30 bar).

Not all the refrigerant escapes.

Certain versions feature a transparent plastic disc which breaks off as soon as the valve responds.

Scheme 18

1. Evaporator
2. Expansion valve
3. Valve for extraction, charging and measurement
4. Inspection port (not installed with R134a circuits)
5. Receiver with dryer
6. Condenser
7. Compressor

Note. Arrows show direction of refrigerant flow.

Scheme 19

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

Note. Arrows show direction of refrigerant flow.

Refrigerant Circuit Quick-Release Connections

1. Only valves and connections resistant to R134a refrigerant and the related refrigerant oils are to be used.
2. There are different connections (OD) for high and low pressure sides.
3. Discharge refrigerant circuit before removing valves or valve inserts.
4. Always screw on sealing caps.

Arrangement in vehicle --> 87 - AIR CONDITIONING

Connections with Schrader Valve

Scheme 20

A - Service connection (soldered in)

B - Schrader valve insert

C - O-ring (for valve)

D - Cap with seal

Connections with Primary Sealing Valve

Connection with High-Pressure Valve

Scheme 21

1. Socket with external or internal thread
2. O-ring: 10.8 mm; 1.8 mm, identification: black or colored
3. Valve with groove for O-ring and external or internal thread M 8x1 for cap
4. O-ring for cap: 10.8 mm; 1.8 mm, identification: black or colored
5. Cap

Connection with Low-Pressure Valve

1. Socket with external thread and groove for O-ring
2. O-ring: 7.6 mm; 1.8 mm, identification: black or colored
3. Valve internal thread for cap M 8x1
4. O-ring for cap: 7.6 mm; 1.8 mm, identification: black or colored
5. Cap

Refrigerant Circuit Switches, Sensors, and Related Connections

Note. Refer to vehicle-specific refrigerant circuit for switching pressures, switch removal/installation and switch layout/design --> 87 - AIR CONDITIONING .

Scheme 22

Function

Switches coolant fan up to next speed setting in the event of pressure increase (approx. 16 bar) in refrigerant circuit.

A/C Refrigerant High Pressure Switch F118

Function

Switches off compressor in the event of excess pressure in the refrigerant circuit (approx. 32 bar).

Scheme 23

Function

Switches off compressor in the event of pressure drop in the refrigerant circuit (approx. 2 bar).

Connections with Valve for Refrigerant Circuit Switches

1. There are different threads for switches on high and low pressure sides.

Scheme 24

1. Only valves and O-rings resistant to R134a refrigerant and the related refrigerant oils are to be used.

A - Connection (soldered in)

B - O-ring

C - Valve (with O-ring)

Scheme 25

This pressure switch has 3 functions

1. Switches coolant fan up to next speed setting in the event of pressure increase (approx. 16 bar) in refrigerant circuit.

2. Switches off air conditioner in the event of excessive pressure (approx. 32 bar) caused for example by inadequate engine cooling.

3. Switches off air conditioner in the event of insufficient pressure (approx. 2 bar) caused for example by loss of refrigerant.

Note. The A/C Pressure Switch F129 replaces the A/C Refrigerant High Pressure Switch F23 , the A/C Refrigerant Low Pressure Switch F73 and the A/C Refrigerant High Pressure Switch F118.

Scheme 26

The High Pressure Sensor G65 is installed instead of the A/C Pressure Switch F129 or the A/C Pressure/temperature Sensor G395.

The A/C Pressure/temperature Sensor G395 ("grey" housing at present) and the High Pressure Sensor G65 ("black" housing at present) currently only differ in terms of housing color and attention is therefore to be paid to correct assignment on replacement . As these two sensors emit different signals, the relevant control module can only evaluate the signal to which it has been matched.

The High Pressure Sensor G65 generates a square-wave signal or data telegram when voltage is applied. This signal changes with the pressure in the system.

The downstream control modules (coolant fan control module, Engine Control Module (ECM), A/C Control Head E87 , Climatronic Control Module J255 etc.) use this signal to calculate the pressure in the refrigerant circuit and to actuate the coolant fans, fan motor and A/C Clutch N25 accordingly or to modify actuation of the A/C Compressor Regulator Valve N280.

A/C Pressure/Temperature Sensor G395

The A/C Pressure/temperature Sensor G395 is installed instead of the High Pressure Sensor G65.

Externally, the A/C Pressure/temperature Sensor G395 ("grey" housing at present) and the High Pressure Sensor G65 ("black" housing at present) currently only differ in terms of housing color and attention is therefore to be paid to correct assignment on replacement . As these two sensors emit different signals, the relevant control module can only evaluate the signal to which it has been matched.

When voltage is applied, the A/C Pressure/temperature Sensor G395 exchanges information via the air conditioner data bus system ("LIN bus") with the corresponding control module. The relevant control module uses this information to calculate the pressure and temperature in the refrigerant circuit and any faults detected are signalled to the control module.

The temperature measured by the A/C Pressure/temperature Sensor G395 differs on account of the design of the A/C Pressure/temperature Sensor G395 and the component location from the actual temperature of the refrigerant in the refrigerant circuit. It is therefore not evaluated at present by all control modules and used for air conditioner control.

This information is used for example by the control head, Climatronic Control Module J255 to calculate the pressure in the refrigerant circuit and to actuate the downstream control modules (coolant fan control module, Engine Control Module (ECM) etc.) by way of the data bus system. These control modules then regulate, for example, the coolant fans and engine accordingly --> 87 - AIR CONDITIONING .

Scheme 27

The regulator valve is installed in the compressor. It is actuated by the A/C Control Head E87 or the Climatronic Control Module J255. The pressure on the low pressure side is influenced by way of the regulator valve, thus regulating the temperature in the evaporator.

Note. The A/C Compressor Regulator Valve N280 is part of the compressor and cannot be replaced separately.

Scheme 28

Inductive sensor

The sensor pulses (4 per compressor revolution) and the engine speed enable the A/C Control Head E87 or the Climatronic Control Module J255 to calculate belt slip.

If the belt slip exceeds a specified value, the compressor is switched off by the control module via the A/C clutch.

Note. The sensor is installed in Audi vehicles with compressor drive via poly V-belt and Zexel compressor.

Scheme 29

The Refrigerant Temperature Sensor (with temperature-dependent resistor) is installed e.g. in high pressure line in vicinity of the compressor.

In the refrigerant circuit, there is a direct relationship between temperature and pressure, if there should be too little refrigerant in the refrigerant circuit, the temperature in the refrigerant circuit rises higher than intended for this pressure while A/C system is running.

Note. Installed e.g. in the Audi Q7 with specific engines --> 87 - AIR CONDITIONING and --> Electrical Wiring Diagrams, Troubleshooting and Component Locations The A/C control head, Climatronic Control Module J255 evaluates pressure and temperature in the refrigerant circuit and switches off the compressor in the event the temperature increases above the value stored for this pressure --> 87 - AIR CONDITIONING and in the Guided Fault Finding function of A/C system

Coolant Fan Control Module J293

(Not on refrigerant circuit)

Scheme 30

This control module switches the A/C clutch and thus the compressor on and off. It switches the coolant fans and calculates the pressure in the refrigerant circuit on vehicles with High Pressure Sensor G65 --> Electrical Wiring Diagrams, Troubleshooting and Component Locations and --> 87 - AIR CONDITIONING .

Refrigerant Circuit Pressures and Temperatures

The pressures and temperatures in the refrigerant circuit depend on the instantaneous operating statuses (e.g. engine speed, coolant fan speed 1, 2, or 3, engine temperature, compressor on or off) as well as environmental influences (e.g. ambient temperature, humidity, required cooling output).

On vehicles with A/C Compressor Regulator Valve N280 the pressure on the low pressure side is altered by actuating the valve.

For this reason, the values given in the following table are only intended as a rough guide. They are attained at an engine speed of 1500 to 2000 RPM and an ambient temperature of 20 C after about 20 minutes.

Refer to vehicle-specific refrigerant circuit for locations of pressure gauge connections --> 87 - AIR CONDITIONING .

At 20 C with the engine not running, the pressure in the refrigerant circuit is 4.7 bar. Refer to --> Air Conditioning System Principles

Note. Pressure is measured in different units: 1 MPa (mega pascal) corresponds to 10 bar positive pressure or 145 psi, 1 bar absolute pressure corresponds to 0 bar positive pressure and thus to the ambient pressure (atmospheric pressure).

Refrigerant Circuit with Expansion Valve

HP (HD) High pressure side of refrigerant circuit

LP (ND) Low pressure side of refrigerant circuit

* 1 - The pressure in a refrigerant circuit with regulating compressor is maintained at approx. 2 bar absolute pressure (corresponds to approx. 1 bar positive pressure) despite varying heat transfer and fluctuating engine speeds. This however only applies within the output range of the compressor. If the output limits of the compressor are exceeded, the pressure will rise --> Refrigerant Circuit, Checking Pressures with A/C Service Station .

* 2 - The temperature in a refrigerant circuit with regulating compressor is maintained within the regulating range of the compressor despite varying heat transfer and fluctuating engine speeds. This however only applies within the output range of the compressor. If the output limits of the compressor are exceeded, the temperature will rise --> Refrigerant Circuit, Checking Pressures with A/C Service Station .

Note. Non self-regulating compressors are switched off by the relevant control module via the A/C Compressor Regulator Valve N280 at evaporator temperatures below 0 C. On vehicles with A/C Compressor Regulator Valve N280 the pressure on the low pressure side is altered by actuating the valve. Temperature and pressure in the refrigerant circuit in vehicles with two evaporators and two expansion valves correspond to those in vehicles with only one evaporator and one expansion valve (parallel switching).

Arrows show direction of refrigerant flow.

HD- High Pressure (HP) side of refrigerant circuit.

ND- Low Pressure (LP) side of refrigerant circuit.

Scheme 31

1 - Evaporator

2 - Expansion valve

3 - High pressure switch/high pressure sensor

1. Different versions depending on vehicle

4 - Service connection, HP (HD) side

5 - Receiver

1. Different versions depending on vehicle

6 - Condenser

7 - Pressure relief valve

8 - Compressor, HP (HD) side

9 - Compressor, LP (ND) side

10 - Pre-volume

1. Not present on all vehicles

11 - Service connection, valve LP (ND)

Refrigerant Circuit with Restrictor and Reservoir

HP (HD) High pressure side of refrigerant circuit

LP (ND) Low pressure side of refrigerant circuit

The pressures on the low pressure side are maintained at approx. 2 bar absolute pressure (corresponds to approx. 1 bar positive pressure) by the "regulating" compressor even at varying engine speeds. This however only applies within the output range of the compressor. If the output limits of the compressor are exceeded, refer to --> Refrigerant Circuit, Checking Pressures with A/C Service Station .

Note. On vehicles with A/C Compressor Regulator Valve N280 the pressure on the low pressure side is altered by actuating the valve.

Arrows show direction of refrigerant flow.

HD- High Pressure (HP) side of refrigerant circuit.

ND- Low Pressure (LP) side of refrigerant circuit.

Scheme 32

1 - Compressor, HP (HD) side

2 - Condenser

3 - Restrictor

4 - Evaporator

5 - Reservoir

6 - Compressor, LP (ND) side

Scheme 33

Pressure gauge scales

1. Temperature scale for refrigerant R134a CF3 CH2F or CH2F CF3
2. Pressure scale

Note. Pressure is measured in different units: 1 MPa (mega pascal) corresponds to 10 bar positive pressure or 145 psi, 1 bar absolute pressure corresponds to 0 bar positive pressure and thus to the ambient pressure (atmospheric pressure).

In addition to the pressure scale, pressure gauges may have one or more temperature scales. The scale values for R134a are assigned according to the vapor pressure table. As different refrigerants develop different vapor pressures at the same temperature, each temperature scale is marked for the appropriate refrigerant.

a Refrigerant circuit pressure and temperature measurements

1. The high-pressure gauge measures the pressure and temperature distributed evenly from the compressor outlet via the condenser to the constriction (restrictor or expansion valve) when the air conditioning system is switched on.
2. The low-pressure gauge measures the pressure and temperature distributed evenly from the constriction (restrictor or expansion valve) via the evaporator to the compressor inlet when the air conditioning system is switched on.

Note. The relationship between pressure and temperature indicated on the gauges only exists in a refrigerant circuit containing liquid or vapor, but not gas. In the gas state, the temperature is approx. 10 C to 30 C higher than the gauge reading.

b Verification of refrigerant in a closed vessel

Refrigerant R134a is present in a closed vessel or refrigerant circuit if the temperature reading on the gauge corresponds to the temperature of the refrigerant (standing liquid assumes the temperature of its surroundings).

A closed vessel or deactivated refrigerant circuit is empty if the temperature indicated on the gauge is below that of the refrigerant.

Note. The relationship between pressure and temperature indicated on the gauges no longer applies if no liquid is present and the pressure is built up solely by gas.

Pressure Gauges permit the following tests and measurements

Service and Recycling Units

Service units for the extraction, cleaning and transfer of refrigerant for motor vehicle air conditioning systems are currently available from various manufacturers.

Certain A/C service stations (with appropriate auxiliary device and different adapters if necessary) can also be used for flushing the refrigerant circuit --> Refrigerant Circuit, Flushing with Refrigerant R134a

Classification of Extraction Systems

Note. The service and recycling units used in motor vehicle workshops are extraction and charging systems not requiring a permit (Group "3") but which are only to be operated by qualified personnel. Instructions for unit operation and maintenance can be found in the relevant manufacturers documentation. Extraction and charging systems of groups "1" and "2" are not used in motor vehicle workshops.

Group "3" extraction and charging systems

Mobile extraction and charging systems for filling compressed-gas vessels permanently connected to the system

The refrigerant or refrigerant/oil mixture is transferred to compressed-gas vessels which are permanently connected to the mobile systems. In line with 3 Para. 5 No. 3 of the German pressure vessel regulations (different regulations may apply in other countries), compressed-gas vessels are classified as pressure vessels in this case.

The charging systems

1. Do not require a permit
2. Do not require expert testing, as the gas is transferred to compressed-gas vessels which are classed as being pressure vessels (systems used for transfer from these pressure vessels to compressed-gas vessels for supplying to third parties do however require a permit and are subject to mandatory testing)

Charging Systems Not Requiring a Permit

Charging systems not requiring a permit are ones used for transferring compressed gases to mobile compressed-gas vessels for internal use only.

Note. Some service units are charging systems not requiring a permit. When working with such equipment, the refrigerant is not transferred to mobile compressed-gas vessels, but rather into a permanently installed charging cylinder with visible level gauge and float switch.

Recommendation

It is advisable to use a portable cylinder with visible level gauge and pressure relief valve for surplus refrigerant for internal use.

Attention must be paid in Germany to TRG 402 (technical regulations for compressed gases) when transferring compressed gases to other compressed-gas vessels (different regulations may apply in other countries).

Refrigerant Circuit Repair Information

Special tools and accessories

Scheme 34

The performance of proper workmanlike repairs on an air conditioning system

1. Requires the use of special tools and materials as listed in --> «Testing Equipment, Tools and Materials»(ref-289226-S08148975042008062700000) .
2. Requires compliance with the basic instructions for use of leak detectors --> «Refrigerant Circuit, Determining Leaks»(ref-289226-S04805314442008062700000) .
3. Requires expert knowledge.

Note. Releasing refrigerant into the environment is prohibited --> Laws and Regulations (laws and regulations).

Refrigerant Circuit

> Important Repair Notes

> Refrigerant Circuits, Converting from R12 Refrigerant to R134a

> Working with A/C Service Station

> Refrigerant Circuit, Discharging with A/C Service Station

> Refrigerant Circuit, Evacuating with A/C Service Station

> Refrigerant Circuit, Charging with A/C Service Station

> Air Conditioner, Starting after Charging

> Transferring Refrigerant to Charging Cylinder or Reservoir Bottle

> A/C Service Station, Draining

> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen

> Refrigerant Circuit, Flushing with Refrigerant R134a

> Refrigerant Circuit, Determining Leaks

Important Repair Notes

1. Air conditioning systems designed for refrigerant R12 are only to be filled with refrigerant R134a if certain requirements are fulfilled. Refer to --> «Refrigerant Circuits, Converting from R12 Refrigerant to R134a»(ref-289226-S17331453902008062700000) .
2. The refrigerant oils specifically developed for R134a and R12 refrigerant circuits are never to be mixed.
3. A/C service stations which come in contact with the refrigerant are only to be used for the intended refrigerant.
4. Components of R134a refrigerant circuits can be recognized from their labelling, green stickers or design (e.g. different threads) to prevent interchange with components for refrigerant R12.

1. A label indicating the refrigerant used is provided in the engine compartment on the lock carrier or in the plenum chamber.
2. Different refrigerants are never to be mixed.

Note. When working on the refrigerant circuit, always pay attention to the information given in the Sections on "Safety measures" --> R134a Safety Precautions and "Basic rules for working on refrigerant circuit" --> Basic Rules for Working on Refrigerant Circuit .

Refrigerant Circuits, Converting from R12 Refrigerant to R134a

CFC refrigerants are no longer used in the automotive industry.

Converting refrigerant circuits from R12 to R134a and servicing converted circuits

Working with A/C Service Station

Important Notes

Observe the following with regard to A/C service station operation (e.g. V.A.G 1885)

1. The filters and dryers installed must be replaced at the latest on completion of the service life specified in the relevant operating instructions.
2. If an A/C service station is also used for flushing the refrigerant circuit, dryer and filter must be replaced in shorter intervals --> «Refrigerant Circuit, Flushing with Compressed Air and Nitrogen»(ref-289226-S00981775572008062700000) .
3. Exclusive use is to be made of refrigerant oils which have been approved for the vehicle-specific refrigerant circuit (if necessary, fill refrigerant oil directly into refrigerant circuit).

Extracted refrigerant is not to be reused if there is any doubt about the composition of the refrigerant extracted, even after cleaning in the A/C service station.

1. The A/C service station is to be drained in all these cases --> «A/C Service Station, Connecting»(ref-289226-S19081329602008062700000) , the system cleaned if necessary and the filters, dryers and refrigerant oil replaced.

Commercially available A/C service stations can be classified in 2 groups

1. A. A/C service stations which clean extracted refrigerant for re-use (so-called extraction and recycling stations), e.g. V.A.G 1885 (currently available A/C service stations )
2. B. A/C service stations which transfer extracted refrigerant to recycling containers (for large-scale recycling). These are referred to as extraction systems.

Connecting for Measurement and Testing

1. Work procedure may vary depending on the type of tools selected (the tool-specific operating instructions should therefore be followed).

Note. The work procedure is always to be performed as described in the operating instructions for the relevant A/C service station (e.g. V.A.G 1885).

The charging hoses are to be connected as follows to prevent the ingress of air or moisture into the refrigerant circuit

1. Switch off ignition.
2. Connect A/C service station to power supply.
3. Unscrew caps from service connections or connections with valve (refer to vehicle-specific refrigerant circuit) --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) .
4. Evacuate charging hoses if necessary.

1. Connect quick-release coupling to service connection of refrigerant circuit.

Note. Screw valve adapters V.A.G/9 , V.A.G/10 or air conditioning adapter set V.A.G 1786 to refrigerant circuit connections with valve and bleed charging hoses during connection to adapters (faintly audible escape of refrigerant gas is permitted) --> A/C Service Station, Connecting .

Vehicles with one service connection only

1. The charging hose must be installed with a valve opener for opening valve in valve adapter.
2. Only screw handwheel into quick-release coupling adapter to the extent required to reliably open valve in service connection (observe pressure gauge; take care not to strain valve).
3. Start engine and perform planned tests and measurements.
4. Compare values determined to specified measured values --> «Refrigerant Circuit, Checking Pressures with A/C Service Station»(ref-289226-S30223210142008062700000) .

1. Before disconnecting quick-release coupling, close it by screwing out handwheel.

Refrigerant Circuit, Discharging with A/C Service Station

1. Work procedure may vary depending on the type of tools selected (follow tool-specific operating instructions).
2. The refrigerant circuit is to be discharged if parts of the refrigerant circuit are to be removed, if there is any doubt about the quantity of refrigerant in the circuit or if safety precautions so require.
3. All the necessary usage information for working with the refrigerant A/C service station can be found in the A/C service station operating instructions.

Discharging

1. Switch off ignition.
2. Connect A/C service station in line with operating instructions to vehicle service connections (refer to vehicle-specific refrigerant circuit) and start up A/C service station --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) .

Note. There is a possibility of refrigerant oil being extracted from the refrigerant circuit together with the refrigerant. To ensure compressor lubrication, the refrigerant oil in the circuit must be topped up with fresh oil --> Refrigerant R134a/Refrigerant Oil Capacities and Specifications . On vehicles equipped with a compressor with no A/C clutch (with A/C Compressor Regulator Valve N280), the engine should not be run for longer than absolutely necessary with the refrigerant circuit empty and high engine speeds are to be avoided (compressor always in operation as well). On vehicles with a compressor with no A/C clutch, the engine is only to be started following complete assembly of the refrigerant circuit (avoid high engine speeds).

Refrigerant Circuit, Evacuating with A/C Service Station

1. The work procedure is always to be performed as described in the operating instructions for the A/C service station.
2. Quantity of refrigerant oil in circuit checked and if necessary corrected --> «Refrigerant R134a/Refrigerant Oil Capacities and Specifications»(ref-289226-S30103541682008062700000)
3. Quantity of refrigerant in A/C service station checked

The refrigerant circuit must be evacuated before it is filled with refrigerant. Moisture is also extracted from the circuit.

Evacuation

1. Switch off ignition.
2. Connect A/C service station to power supply.
3. Connect charging hoses of A/C service station to vehicle refrigerant circuit with quick-release coupling adapter (refer to vehicle-specific refrigerant circuit) --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) .
4. Screw in handwheel of quick-release coupling adapters until valves of service connections are definitely open (take care not to strain valve).

Note. If pressure is to be measured after charging system on vehicles with a service connection on one side of the refrigerant circuit only, use valve adapter and charging hose with valve opener --> A/C Service Station, Connecting .

1. Switch on A/C service station and evacuate refrigerant circuit for at least 30 minutes. The pressure reading must indicate an absolute pressure of less than 10 mbar (corresponding to 990 mbar vacuum).

Note. At this pressure, both green LEDs light for example on A/C service station V.A.G 1885 (currently available A/C service stations ).

1. Switch off A/C service station and allow to stand for at least 1 hour.

1. If the vacuum display (LED chain) does not change, the system is free of leaks and can be charged.

Note. A current vacuum reading (LED) is only obtained using A/C service station V.A.G 1885 , for example (currently available A/C service stations ) after pressing the "Evacuate" button again.

Scheme 35

1. If with this A/C service station the upper (green) LEDs do not light immediately after switching on, either the refrigerant circuit is leaking or there is still residual moisture/refrigerant in the circuit.

Proceed as follows if the vacuum is not maintained

1. Fill the circuit with 100 g of refrigerant, localize any leaks using leak detector and eliminate accordingly.
2. Evacuate and again observe the vacuum display over a period of hours. Charging may only be performed if vacuum is maintained.

Refrigerant Circuit, Charging with A/C Service Station

Note. The entire refrigerant charge can be added to either the high or low-pressure side --> Refrigerant R134a/Refrigerant Oil Capacities and Specifications . The work procedure is always to be performed as described in the operating instructions for the A/C service station. Before pouring in refrigerant, correct quantity of refrigerant oil --> Refrigerant R134a/Refrigerant Oil Capacities and Specifications .

1. Switch off ignition.
2. Evacuate refrigerant circuit using A/C service station. Refer to --> «Refrigerant Circuit, Evacuating with A/C Service Station»(ref-289226-S11842127552008062700000)
3. Screw out handwheel at quick-release coupling adapter (to close it).
4. Allow refrigerant to flow into charging hose.

1. Take charging cylinder reading.
2. Screw in handwheel at quick-release coupling adapter (to open it) and charge with the specified quantity of refrigerant.
3. Switch off A/C service station.

Air Conditioner, Starting after Charging

Note. If the compressor has been removed, rotate it about 10 times by hand prior to initial start-up to prevent damage caused by liquid impact when first switched on (any oil in compressor cylinder is forced out on rotation).

1. Start engine with compressor switched off (version with A/C clutch).
2. Set compressor to minimum output, i.e. "Econ" or A/C off mode (version with no A/C clutch with regulator valve).
3. Wait until idling speed has stabilized.
4. Switch on compressor and operate system for at least 2 minutes at idling speed.

1. If necessary, check pressures in refrigerant circuit using A/C service station.
2. Switch off engine.
3. Screw out handwheel on quick-release coupling adapter.
4. Disconnect charging hoses from refrigerant circuit.

1. Screw protective caps back on.

Transferring Refrigerant to Charging Cylinder or Reservoir Bottle

1. The work procedure is always to be performed as described in the operating instructions for the A/C service station.
2. A certain quantity of refrigerant is specified as charge for each air conditioning system. To ensure that neither too much nor too little refrigerant is added (either would reduce the cooling output), the charging cylinder has a scale indicating the weight.
3. The volume of a refrigerant changes as a function of pressure. The scale must therefore be set according to the pressure in the charging cylinder.

Note. Do not completely drain the reservoir (charging cylinder or bottle) as the liquid column boundary layer cannot be traced in the tube during filling (outside visible range).

Blowing through Refrigerant Circuit

Note. In the case of vehicles on which the refrigerant pipes have no threads for connection of Adapter set refrig cir R 134a V.A.G 1785 , use e.g. a flushing gun with rubber end piece or an adapter from the adapter case for VW/Audi passenger cars VAS 6338/1 for blowing through the individual components. When using a flushing gun with rubber end piece, take special care not to damage the connections (crushing or scratching). Evaporator is to be flushed by way of connection for low-pressure pipe (large diameter) after removing expansion valve or removing restrictor. Always flush or blow through components in direction opposite to refrigerant flow. Check expansion valve and replace if dirty or corroded. Replace any components on which dark, sticky deposits cannot be removed with compressed air. Flush these components using refrigerant R134a or replace. Thin, light grey deposits on the insides of pipes do not impair the function of the components. After flushing, always replace receiver or reservoir and restrictor. Replace dryer cartridge on condensers on which the dryer cartridge is installed in the integrated receiver.

After blowing through the refrigerant circuit

1. Replace these components depending on equipment (restrictor and reservoir, expansion valve and fluid reservoir or dryer cartridge)
2. Depending on the kind of complaint, replace compressor --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) or drain the remaining refrigerant oil from the compressor removed --> «Refrigerant Circuit Components, Replacing»(ref-289226-S05629535382008062700000) (replace components of refrigerant circuit) and refill the prescribed amount of fresh refrigerant oil --> «Approved Refrigerant Oils»(ref-289226-S30013434552008062700000) (Approved refrigerant oils and capacities for refrigerant oil)

Note. There is a defined and prescribed amount of refrigerant oil in the replacement compressor. If necessary, a certain amount of refrigerant oil must be filled into the circuit in addition on vehicles with two evaporators --> 87 - AIR CONDITIONING and --> Approved Refrigerant Oils (Approved refrigerant oils and capacities for refrigerant oil). If the compressor will not be replaced, the refrigerant oil in the compressor must be topped up to the prescribed amount (pour out refrigerant oil and fill the prescribed amount into the compressor or the refrigerant circuit) --> Refrigerant Circuit Components, Replacing (Replacing components of refrigerant circuit) and --> Approved Refrigerant Oils (Approved refrigerant oils and capacities of refrigerant oil)

1. Reassemble the refrigerant circuit completely --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) .
2. Evacuate and recharge refrigerant circuit according to specification.
3. Start up A/C system according to specification.

Note. On vehicles with restrictor and reservoir, the restrictor and reservoir are removed, the lines disconnected for removing the restrictor are reconnected again. The connections to the reservoir removed are connected by means of two adapters and the fill hose VAS 6338/31 (from the adapter case for VW/Audi passenger cars VAS 6338/1)

Scheme 36

1 - A/C service station

1. With electronics and a program for flushing, e.g. A/C service station with flushing equipment VAS 6336 or A/C service station with flushing equipment VAS 6337
2. If an A/C service station with no flushing program is used, the procedure must be performed manually (evacuating, flushing 3 times with at least 4 kg refrigerant each, extracting the refrigerant, evacuating).

2 - Refrigerant hose of the A/C service station

1. From the high pressure side of the A/C service station (mostly red) to the connection for the low pressure side of the compressor on the refrigerant circuit (larger diameter)

3 - Adapter for connecting low pressure side to refrigerant circuit

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)
2. From the adapter case for VW/Audi passenger cars VAS 6338/1

4 - Connection of low pressure side to refrigerant circuit

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)
2. On refrigerant line from compressor to reservoir

5 - Connection to reservoir

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)
2. On refrigerant line from compressor to reservoir

6 - Adapter for bridging removed reservoir

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)
2. From the adapter case for VW/Audi passenger cars VAS 6338/1

7 - Fill hose for refrigerant --> Adapter for Assembly of Flushing Circuits

1. For example fill hose VAS 6338/31 (from the adapter case for VW/Audi passenger cars VAS 6338/1)

8 - Adapter for bridging removed reservoir

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)
2. From the adapter case for VW/Audi passenger cars VAS 6338/1

9 - Connection to reservoir

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)

10 - Evaporator

11 - Component location of restrictor

1. The restrictor is removed.
2. Removing restrictor --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)

12 - Threaded connections in refrigerant line

1. Thread together again after removing restrictor --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)

13 - Condenser

14 - Connection of high pressure side to refrigerant circuit

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)

15 - Adapter for connection of high pressure side on refrigerant circuit

1. Different versions depending on vehicle --> «Adapter for Assembly of Flushing Circuits»(ref-289226-S04674881082008062700000)
2. From the adapter case for VW/Audi passenger cars VAS 6338/1

16 - Fill hose to flushing device for refrigerant circuits

1. From connection to high pressure side of compressor on refrigerant circuit (smaller diameter) to input of flushing device for refrigerant circuits.

17 - Flushing equipment for refrigerant circuits

1. Different versions and different designs, e.g. flushing equipment for refrigerant circuits VAS 6336/1 or flushing equipment for refrigerant circuits VAS 6337/1
2. With filter, sight glass, safety valve, heating, refrigerant vessel etc. (depending on version).
3. Depending on the A/C service station design and the flushing device for refrigerant circuits, there may be a check valve installed at the output of the flushing device for refrigerant circuits (to ensure the correct flow direction of the refrigerant when flushing).

18 - Refrigerant hose of the A/C service station

1. From the low pressure side of the A/C service station (mostly blue) to the output of the flushing device for refrigerant circuits.

Refrigerant Circuit, Determining Leaks

> Refrigerant Circuit, Tracing Leaks with Electronic Leak Detector V.A.G 1796

> Refrigerant Circuit, Locating Leaks with Leak Detection System VAS 6201

> Leak Detection Additive, Adding with Refrigerant Circuit Charged

> Refrigerant Circuit, Locating Leaks with UV Lamp VAS 6196/4

Refrigerant Circuit, Tracing Leaks with Electronic Leak Detector V.A.G 1796

Minor leaks can be detected using an electronic leak detector or UV leak detector lamp for example.

Note. Currents of air quickly disperse refrigerant gas. Draughts must therefore be avoided during leak detection. If the refrigerant circuit is completely empty, charge with about 100 g of refrigerant.

Leak detection

1. Start up leak detector in line with relevant operating instructions.
2. Always hold test probe beneath suspected leak.

Depending on the model, leak detection is indicated by an increase in clicking rate or a warning tone (refer to operating instructions for leak detector).

Refrigerant Circuit, Locating Leaks with Leak Detection System VAS 6201

Note. Certain leaks are difficult or even impossible to locate using an elect. leak detector. In such cases, use can be made of the leak detection system VAS 6201. Refrigerant circuit leaks result in a loss of refrigerant oil together with the refrigerant. This oil generally remains in the vicinity of the leak location. Adding a small quantity of fluorescent fluid to the refrigerant circuit makes this oil visible under UV light. The fluid (PAG oil containing an additive which shows up under UV light) is poured into the refrigerant circuit and becomes distributed with the refrigerant oil when the air conditioner is switched on. The air conditioner must be operated for at least 60 min. to distribute the additive throughout the refrigerant circuit (compressor must run). The refrigerant oil containing the additive (which shows up under UV light) can either be poured directly into the open circuit or pumped in with the circuit charged using the hand pump VAS 6201/1 (from leak detection system VAS 6201) via the service connection on the low-pressure side. If the leak detection additive is applied via the service connection on the low-pressure side with the refrigerant circuit charged, a small quantity of additive remains in the service connection. This is to be carefully removed so as to avoid subsequent erroneous leak detection. If a component forming part of a circuit into which the leak detection additive is poured has to be replaced, thoroughly clean joints with other components after assembling refrigerant circuit. Otherwise, the remnants could lead to erroneous leak detection. On discharging the refrigerant circuit, refrigerant oil and thus also leak detection additive enters into the A/C service station. The oil is removed from the refrigerant in the oil separator of the A/C service station and discharged from the A/C service station via the drain. The refrigerant oil drained off is not to be poured back in. It is to be replaced with fresh refrigerant oil. Pay attention to the following if leak detection fluid has already been poured into a refrigerant circuit in the course of previous repair work: Only add new leak detection fluid if refrigerant oil is replaced. If only some of the refrigerant oil has been replaced, just add the corresponding quantity of leak detection fluid. If, for example, 100 ml of refrigerant oil has been replaced on a vehicle containing 250 ml, only add 1 ml (cm 3 ) of leak detection additive. Certain materials and their compounds (e.g. oxidation products on aluminum components, anti-corrosion waxes) also show up under UV light.

Tools and other items required

Scheme 37

1. Hand pump with low-pressure service hose, service coupling and non-return valve VAS 6201/1
2. Cartridge VAS 6201/2
3. Cleaning agent VAS 6201/3
4. UV leak detection lamp VAS 6201/4
5. UV-absorbing safety goggles VAS 6201/6
6. Sticker VAS 6201/7
7. Tube VAS 6201/8 VAS 6201/8
8. Protective gloves VAS 6201/9

Pouring in leak detection additive with refrigerant circuit empty

Scheme 38

The cartridge - A - contains 15.4 ml of leak detection additive (one unit - B - corresponds to 2.5 ml).

Scheme 39

1. Assemble hand pump VAS 6201, item - 1 - with cartridge, item - 2 - VAS 6201/2.
2. Insert tube VAS/8 (--> (Scheme 39) VAS 6201/8 item - 7 -) in hand pump.
3. Open hand pump service valve.

Scheme 40

With refrigerant circuit empty, the leak detection additive can best be poured in via an open connection.

1. Open the refrigerant circuit at a readily accessible connection.
2. Cover the surrounding area with sheeting or absorbent paper.
3. Hold tube upwards.
4. Screw in toggle of hand pump until leak detection additive emerges from tube.

1. Fill the refrigerant circuit with 2.5 + / - 0.5 ml (milliliter = cm 3 ) of leak detection additive.
2. Replace O-ring at open connection.
3. Assemble refrigerant circuit.
4. Affix sticker next to service connections to indicate that leak detection fluid has been added to the refrigerant circuit.

1. Evacuate and charge refrigerant circuit as specified.

Note. Pay attention to the following if leak detection fluid has already been poured into a refrigerant circuit in the course of previous repair work: Only add new leak detection fluid if refrigerant oil is replaced. If only some of the refrigerant oil has been replaced, just add the corresponding quantity of leak detection fluid. If, for example, 100 ml of refrigerant oil has been replaced on a vehicle containing 250 ml, only add 1 ml (cm 3 ) of leak detection additive. The air conditioner must be operated for at least 60 min. to distribute the additive throughout the refrigerant circuit (compressor must run). Depending on the magnitude and location, it may take several days for sufficient refrigerant oil and additive to emerge to clearly identify the leak.

Leak Detection Additive, Adding with Refrigerant Circuit Charged

Note. Pay attention to the following if leak detection fluid has already been poured into a refrigerant circuit in the course of previous repair work: Only add new leak detection fluid if refrigerant oil is replaced. If only some of the refrigerant oil has been replaced, just add the corresponding quantity of leak detection fluid. If, for example, 100 ml of refrigerant oil has been replaced on a vehicle containing 250 ml, only add 1 ml (cm 3 ) of leak detection additive. A small quantity of leak detection additive remains in the service connection. This is to be carefully removed so as to avoid subsequent erroneous leak detection. The air conditioner must be operated for at least 60 min. to distribute the additive throughout the refrigerant circuit (compressor must run). Depending on the magnitude and location, it may take several days for sufficient refrigerant oil and additive to emerge to clearly identify the leak.

The cartridge - A - contains 15.4 ml of leak detection additive (one unit - B - corresponds to 2.5 ml).

1. Switch off ignition.
2. Remove cap from service connection on low-pressure side of refrigerant circuit.

1. Assemble hand pump VAS 6201, item - 1 - with cartridge, item - 2 - VAS 6201/2.
2. Insert tube VAS 6201/8 (--> (Scheme 39) VAS 6201/8 item - 7 -) in service coupling and open service coupling by screwing in handwheel. Hold hose upwards and screw in toggle of hand pump until leak detection additive starts to emerge from tube.

Note. Make sure hand pump hose is completely filled with refrigerant.

1. Close service coupling and remove tube from locking mechanism.

Scheme 41

1. Cover area around service connection on vehicle with sheeting or absorbent paper.
2. Connect filler unit to refrigerant circuit service connection on vehicle.
3. Open service connection by screwing in handwheel.
4. Screw in toggle of hand pump to transfer 2.5 + /- 0.5 ml (milliliter= cm 3 ) of leak detection additive to refrigerant circuit.

Scheme 42

1. Disconnect filler unit from service connection.
2. Use absorbent paper, for example, to remove remnants of leak detection additive from service connection.
3. Seal service connection with cap.
4. If necessary, use cleaning agent to clean area around service connection.

1. Affix sticker next to service connections to indicate that leak detection fluid has been added to the refrigerant circuit.

Refrigerant Circuit, Locating Leaks with UV Lamp VAS 6196/4

Note. After filling, the air conditioner must be operated for at least 60 min. to distribute the additive throughout the refrigerant circuit (compressor must run/be actuated). Depending on the magnitude and location, it may take several days for sufficient refrigerant oil and additive to emerge to clearly identify the leak. In the event of leaks at the evaporator, the additive may be washed out with the condensate and emerge via the condensate drain. As on most vehicles the evaporator is not accessible without considerable effort, checking the condensate drain for example can provide an indication of evaporator leakage. This does however require the additive to have been in the refrigerant circuit for a lengthy period (several days). The safety goggles are not only designed to provide eye protection. They also make the additive more readily visible under UV light. Depending on the accessibility of various parts of the refrigerant circuit, it may be necessary to remove certain vehicle components (e.g. bumper or air cleaner).

Scheme 43

1. Move vehicle to a less brightly lit area of the workshop (daylight or bright artificial lighting diminishes the effect of the UV light).
2. Check accessibility of various parts of the refrigerant circuit and remove components in area of refrigerant circuit which would block view of refrigerant circuit components (e.g. noise insulation and bumper).
3. Wear safety goggles to protect eyes.
4. Connect UV lamp to a 12V battery (vehicle battery). Take care to ensure correct polarity of connections.

1. Switch on UV lamp and illuminate components of refrigerant circuit. Locations at which leakage has resulted in the emergence of refrigerant, refrigerant oil and thus also leak detection additive show up under UV light (fluorescent).

Possible Refrigerant Circuit Concerns

Test requirements

1. Electrical system, vacuum system and air duct fault-finding has not revealed any faults , air conditioner Guided Fault Finding function --> Electrical Wiring Diagrams, Troubleshooting and Component Locations and --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)
2. No fault revealed by air conditioner On Board Diagnostic (OBD) (e.g. using fault read out device V.A.G 1551 --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) or , air conditioner Guided Fault Finding function); no compressor shutoff criterion displayed in measured value block (vehicles with "air conditioner" On Board Diagnostic (OBD) only)

Possible Concerns

Note. For all complaints marked *, refer to --> Refrigerant Circuit, Checking Pressures with A/C Service Station . If a malfunction occurs at only one evaporator in vehicles with two evaporators, also check pressures in the refrigerant circuit. Total cooling system failure * Insufficient cooling output at all vehicle or engine speeds * No or insufficient cooling after driving a few miles * No cooling or insufficient cooling at one or both evaporator(s) (on vehicles with two evaporators).* Compressor, A/C Clutch N25 or A/C Compressor Regulator Valve N280 shut off by pressure switch (e.g. A/C Refrigerant Low Pressure Switch F73 , A/C Refrigerant High Pressure Switch F118 , A/C Pressure Switch F129 or A/C Control Head E87 or Climatronic Control Module J255) on account of excessive or inadequate pressure * No or sharp decrease in fresh-air supply after driving several miles (evaporator iced up) *

Other possible problems

Compressor noise

1. Re-tighten securing bolts for compressor and compressor bracket using a torque wrench.
2. Check routing of refrigerant pipes; they must not touch other components and must not be subject to strain (align if necessary).

Noise (refrigerant hammer) occurring immediately after switching on air conditioner and/or when cornering or braking

1. Discharge, evacuate and recharge refrigerant circuit (too much refrigerant in circuit).

Note. Too much refrigerant oil in the circuit may also result in this problem (no adjustment of refrigerant oil quantity, for example, on replacing compressor).

Water sprays out of vents (in instrument panel or footwell) although air conditioning system is otherwise functioning properly

1. Check proper routing of condensate drain; it must not be crushed or kinked.
2. Check condensate drain valve; it must not be gummed up with wax or underseal and must close properly.
3. Check plenum chamber cover; it must not be damaged and must be properly installed (to stop water running into evaporator).
4. Check water drains in plenum chamber; they must not be blocked (e.g. by leaves).

A/C Service Station, Connecting

Vehicles with Connection on Low- and High-Pressure Side of Refrigerant Circuit

1. Switch off ignition.
2. Connect A/C service station to power supply.
3. Connect quick-release coupling adapter to charging hoses of A/C service station (handwheels not screwed in/hand shut-off valve not open).
4. Switch on A/C service station and evacuate charging hoses (only necessary if there is air in hoses).

1. Switch off A/C service station.
2. Unscrew caps from service connections (with valve).
3. Connect A/C service station via service connections with quick-release coupling adapters to vehicle refrigerant circuit.
4. Screw in handwheel of quick-release coupling adapters until valves are definitely open at refrigerant circuit connection (observe pressure gauge, do not strain valves).

1. Perform planned tests and measurements.

Vehicles with no Connection on Low-Pressure Side of Refrigerant Circuit

On the following vehicles, no service connection is provided for the A/C service station on the low-pressure side of the refrigerant circuit. Adapters are required for connecting the A/C service station to the refrigerant circuit of these vehicles.

1. Audi 80, Audi Cabrio, Audi Coupe
2. Audi A4 up to 07.96
3. Audi 100/Audi A6 up to 03.97
4. Audi A8 up to 11.97

Note. On vehicles with no or inaccessible connection at compressor, remove A/C Refrigerant Low Pressure Switch F73 (jumper contacts in connector for A/C Refrigerant Low Pressure Switch F73) and screw adapter to this connection --> 87 - AIR CONDITIONING .

Note. The tools listed below are commercially available or can be obtained from regional sales center/importer. Should it be necessary to measure pressures at switch connections on high-pressure side, make use of adapter from adapter set for refrigerant circuit V.A.G/9 and proceed in the same manner.

Connecting with Air Conditioning Adapter Set V.A.G 1786

Scheme 44

A - Connection with valve (small valve insert) on low-pressure side of refrigerant circuit

B - Adapter with union nut V.A.G/1

C - Commercially available charging hose (short version with 5/8" thread on each end)

D - Adapter with service connection V.A.G/2 (for connection of quick-release coupling of A/C service station - E -)

Note. Assemble adapter and charging hose as shown and connect first to connection with valve - A -. Adapter with union nut V.A.G/1 is only to be used at connections with "small" valve insert (standard for connection with valve for A/C Refrigerant Low Pressure Switch F73 and also gradually introduced as of 10.94 at compressor). Instead of adapter with union nut V.A.G/1 , use can also be made of adapter V.A.G/10 (remove valve from adapter V.A.G/10 or install valve opener in charging hose).

Connecting with Adapter VAG/10

Scheme 45

1. Unscrew cap from connection with valve - A - (at compressor).
2. Attach O-ring - B - to connection (8.9 mm; 1.8 mm).
3. Screw adapter V.A.G/10 - C - to connection - B -.
4. Install valve opener - D - with appropriate seal in charging hose connection.

Note. The type of valve opener - D - and seals required depends on the charging hose used (specific to manufacturer). The quick-release coupling adapter is not required for connection on the low-pressure side of Audi vehicles. Screw charging hose - E - (to A/C service station) to adapter V.A.G/10.

Note. To minimize the amount of air and moisture penetrating into the charging hoses and thus into the refrigerant circuit, the charging hoses should be connected together as illustrated.

Scheme 46

A - Charging hose to A/C service station

B - Hand shut-off valve

C - Charging hose (short version) with valve opener for connection to adapter - D

D - Adapter V.A.G/10

E - Charging hose (short version) with quick-release coupling adapter (for vehicles with quick-release coupling adapter on low-pressure side)

1. Perform planned tests and measurements.

Refrigerant Circuit, Checking Pressures with A/C Service Station

Note. All test conditions marked * are vehicle-specific and are described in the article for the relevant vehicle. Check cooling output. Connections with valve and service connections for measurement and testing --> 87 - AIR CONDITIONING

Under certain operating conditions, residual moisture in the coolant circuit may lead to the formation of ice on the compressor regulator valve. Such ice formation impedes compressor control. The evaporator is cooled excessively and ices up. Icing-up of the evaporator may be the cause of the following problems

1. Repeated or sporadic failure of the air conditioner (no cooling/heating output) after a lengthy journey; operation of air conditioner soon returns to normal after switching off engine
2. Windows mist up on inside after a lengthy journey and situation is initially not even remedied by pressing "Defrost" button; air conditioner operation soon returns to normal after switching off engine

Corrective action

1. In the case of vehicles as of Model Year 2001 and a compressor with A/C Compressor Regulator Valve N280 , read measured value of evaporator outflow temperature Evaporator Vent Temperature Sensor G263 (by way of function "Reading measured value block"). If sensor measured value is too low under usage conditions outlined by customer (at ambient temperature above 0 C, colder than 0 C for lengthy period although A/C Compressor Regulator Valve N280 not actuated) or too high (greater than approx. 10 C although air conditioner is functioning properly), evaporator may ice up due to the incorrect measured value , air conditioner "Guided Fault Finding function and --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) .
2. On vehicles with no Evaporator Vent Temperature Sensor G263 use Footwell Outlet Temperature Sensor G192 for example to check vent temperature under the usage conditions described by the customer in the following settings: "Lo temperature" for drivers and passengers side, 4 or 5 bars for fresh-air blower speed, air outlet to footwell and fresh-air mode. If measured value of sensor is too low (at ambient temperature above 0 C, colder than 0 C for lengthy period)
3. Check refrigerant pipe between evaporator and reservoir (thick pipe, low-pressure side) with engine running. If pipe is severely iced up when problem occurs (thin ice layer is permissible), this is a further indication that the temperature in the evaporator is too low.
4. Discharge refrigerant circuit, replace reservoir or receiver with dryer and then evacuate refrigerant circuit for at least 3 hours.

Test Conditions

1. Radiator and condenser clean (clean if necessary)
2. Thermal insulation at expansion valve OK and properly installed*
3. Poly V-belt OK and properly tensioned/belts for compressor and alternator OK and properly tensioned*
4. All air ducts, covers and seals OK and properly installed

1. Electrical system and vacuum system fault-finding has not revealed any faults* , air conditioner Guided Fault Finding function and --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)
2. Air conditioner On Board Diagnostic (OBD) has not revealed any faults (with engine running and air conditioner switched on), no compressor shutoff criterion displayed in measured value block (vehicles with "air conditioner" On Board Diagnostic (OBD) only)* , air conditioner Guided Fault Finding function and --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)
3. Air flow through dust and pollen filter not impeded by contamination*
4. Air conditioner unit not drawing in secondary air at maximum fresh-air blower speed; evaporator and heater not drawing in secondary air at maximum fresh-air blower speed*

1. Air flaps in air conditioner unit, heater and evaporator reach end position*
2. Fresh-air intake ducts beneath hood and in passenger compartment as well as corresponding water drain valves OK* --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)
3. Engine warm
4. Vehicle not exposed to sunlight --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000)

1. Ambient temperature above 15 C
2. All instrument panel vents open

1. Start engine.

Settings on A/C Control Head E87 or Climatronic Control Module J255 (and Rear A/C Control Head (Climatronic) E265 in vehicles with two A/C units)

1. Preselect "Auto" mode (compressor on).
2. Set "LO" temperature for drivers and front passengers side (and left and right rear seats in vehicles with two A/C units).

Settings on heater controls

1. Press A/C button and "Rec" or recirculated air button.
2. Turn rotary temperature control towards "Cold" stop.
3. Set rotary fresh-air blower control to "4".

The following system test conditions should then be met

1. Operation of Coolant Fan(s) V7 (at least speed 1)*

Note. With some versions, the fan is not switched on until the pressure in the refrigerant circuit has exceeded a specified value. Operation of Fresh Air Blower V2 (and Rear Fresh Air Blower V80 in vehicles with two A/C units) at maximum speed Recirculated/fresh-air flap set to "Recirculated air mode" (within 1 min. after starting vehicle, air flow flap is closed and recirculated-air flap opened)* Coolant shutoff valve closed* Valves of pump valve unit closed and no coolant circulation pump delivery* Compressor is actually driven (A/C Clutch N25 energized, overload safeguard (if installed) not tripped)*

Pressures, Checking

1. Switch off ignition.
2. Connect A/C service station --> «A/C Service Station, Connecting»(ref-289226-S19081329602008062700000) .
3. Take pressure gauge readings (two possible results).

Note. Temperature of refrigerant circuit components should be equal to ambient temperature (pressure will deviate from values in table if individual components of refrigerant circuit are warmer or colder). At absolute pressure, 0 bar corresponds to an absolute vacuum. Normal atmospheric pressure corresponds to 1 bar absolute. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of 1 bar (can be seen from -1 bar mark below 0). On vehicles with High Pressure Sensor G65 or A/C Pressure/temperature Sensor G395 for which measured pressure is displayed in measured value block, pressure measured should coincide with values in table , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING . Pressure is measured in different units: 1 MPa (mega pascal) corresponds to 10 bar positive pressure or 145 psi, 1 bar absolute pressure corresponds to 0 bar positive pressure and thus to the ambient pressure (atmospheric pressure).

Pressure in refrigerant circuit lower than indicated in table

Not enough refrigerant in circuit

1. Determine whether refrigerant circuit is leaking --> «Refrigerant Circuit, Determining Leaks»(ref-289226-S04805314442008062700000) .
2. Check pressure relief valve.

If pressure relief valve has responded

1. Check actuation of coolant fans.
2. Check for constricted refrigerant pipe and hose cross-sections caused by inadequate bending radii.
3. Check refrigerant pipes and hoses for external damage.
4. If no fault is found, clean refrigerant circuit (flush using refrigerant R134a --> «Refrigerant Circuit, Flushing with Refrigerant R134a»(ref-289226-S32805393652008062700000) or blow through using compressed air and nitrogen --> «Refrigerant Circuit, Flushing with Compressed Air and Nitrogen»(ref-289226-S00981775572008062700000) )

Pressure in refrigerant circuit in line with table or higher

1. Start engine.
2. Set air conditioning system to maximum cooling output.

Note. On vehicles with A/C Compressor Regulator Valve N280 , control current can be read out in measured value block , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

If compressor is not driven with engine running or regulator valve is not actuated

1. Establish and eliminate cause e.g. by checking air conditioner DTC memory.
2. Observe test conditions.
3. Check power supply for A/C Clutch N25. If OK, service A/C clutch.
4. Check actuation of A/C Compressor Regulator Valve N280 , air conditioner Guided Fault Finding function and --> «87 - AIR CONDITIONING»(ref-289225-S23986356182008062700000) .

Note. If low-pressure switch has been removed to connect A/C service station, jumper electrical connections in relevant connector for pressure measurement. Compressor is driven by engine via A/C Clutch N25. A/C Compressor Regulator Valve N280 is actuated by A/C Control Head E87 or Climatronic Control Module J255 , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Continuation of Test Depending on Design of Refrigerant Circuit

> Pressure Checking, Vehicles with Restrictor and Reservoir with Internally Regulated Compressor

> Pressure Checking, Vehicles with Expansion Valve and Receiver with Internally Regulated Compressor

> Pressure Checking, Vehicles with Restrictor, Reservoir and A/C Compressor Regulator Valve with Externally Regulated Compressor

> Pressure Checking, Vehicles with Expansion Valve, Receiver, and A/C Compressor Regulator Valve with Externally Regulated Compressor

Pressure Checking, Vehicles with Restrictor and Reservoir with Internally Regulated Compressor

Note. Connecting A/C service station --> A/C Service Station, Connecting Observe test conditions --> Refrigerant Circuit, Checking Pressures with A/C Service Station .

1. Set engine speed to 2000 RPM.
2. Observe pressure display (e.g. pressure gauge) of A/C service station.

Note. Switching pressures for refrigerant circuit switches are vehicle-specific. Connection with valve for low-pressure switch or at evaporator is only to be used for vehicles with no service connection on low-pressure side and inaccessible connection at compressor or reservoir (measurement accuracy). Only applies to certain vehicles --> 87 - AIR CONDITIONING .

Specifications

High-pressure side

Increasing from initial pressure (on connecting pressure gauges) to max. 20 bar

Low-pressure side

Scheme 47

Decreasing from initial pressure (on connecting pressure gauges) to value in graph

A - High pressure (measured at service connection) in bar

B - Low pressure (measured at connection with valve at compressor or reservoir) in bar

C - Permissible tolerance range

D - Low pressure (measured at connection with valve for low-pressure switch or at service connection) in bar

E - Permissible tolerance range

Note. If no fault is found in relation to this complaint, clean refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ).

Note. If problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least 3 hours. It is not initially necessary to clean the refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ) when this problem occurs since normally, there is only a small quantity of moisture in the system which can be removed by lengthy evacuation.

Note. Pay attention to the following as regards fault "High pressure normal, low pressure too low" : This fault may cause the evaporator to ice up or the A/C Refrigerant Low Pressure Switch F73 to shut off the compressor although the amount of refrigerant in the circuit is OK. On the Audi 100, Audi A6 (up to and including Model Year 1997) and Audi V8, this fault may result in compressor being shut off by control head (if temperature at fresh-air blower drops below -3 C) --> 87 - AIR CONDITIONING .

Note. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil. If there is too much refrigerant oil in the circuit, drain compressor and replace reservoir. After cleaning the refrigerant circuit (flushing with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ), the correct quantity of refrigerant oil is filled into the circuit --> Approved Refrigerant Oils .

Pressure Checking, Vehicles with Expansion Valve and Receiver with Internally Regulated Compressor

Note. Connecting A/C service station --> A/C Service Station, Connecting Observe test conditions --> Refrigerant Circuit, Checking Pressures with A/C Service Station .

1. Set engine speed to 2000 RPM.
2. Observe pressure display (e.g. pressure gauge) of A/C service station.

Note. Switching pressures and design of refrigerant circuit switches are vehicle-specific. Pressures must be measured at service connections; component locations of these connections are vehicle-specific --> 87 - AIR CONDITIONING .

Specifications

High-pressure side

Increasing from initial pressure (on connecting pressure gauges) to max. 20 bar

Low-pressure side

Scheme 48

Decreasing from initial pressure (on connecting pressure gauges) to value in graph

A - High pressure in bar

B - Low pressure in bar

C - Permissible tolerance range

Note. If no malfunction can be found and air conditioner operation is not OK when test is repeated, clean refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ).

Note. If operation is not OK after cleaning refrigerant circuit (flushing with R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ), expansion valve must be replaced.

Note. It is not initially necessary to clean the refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ) when this problem occurs since normally, there is only a small quantity of moisture in the system which can be removed by lengthy evacuation. If problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least 3 hours.

Note. If air conditioner operation is not OK when test is repeated, re-install old expansion valve, clean refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ). Then replace A/C compressor and receiver.

Note. If air conditioner operation is not OK when test is repeated, re-install old expansion valve, clean refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ). Then replace compressor and receiver. With this fault, evaporator may ice up although quantity of refrigerant in circuit is OK.

Note. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil. If there is too much refrigerant oil in the circuit, the compressor must be drained and the receiver must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ), the correct quantity of refrigerant oil is filled into the circuit --> Approved Refrigerant Oils .

Pressure Checking, Vehicles with Restrictor, Reservoir and A/C Compressor Regulator Valve with Externally Regulated Compressor

Note. Connecting A/C service station --> A/C Service Station, Connecting Observe test conditions --> Refrigerant Circuit, Checking Pressures with A/C Service Station .

1. Set engine speed to 2000 RPM.
2. Observe pressure display (e.g. pressure gauge) of A/C service station.

Note. Switching pressures for actuation of A/C Compressor Regulator Valve N280 and Coolant Fans V7 are vehicle-specific. Pressures must be measured at service connections; component locations of these connections are vehicle-specific --> 87 - AIR CONDITIONING .

Specifications

High-pressure side

Increasing from initial pressure (on connection of pressure gauges) to 20 bar

Low-pressure side

Scheme 49

Decreasing from initial pressure (on connecting pressure gauges) to value in graph

A - Low pressure (measured at service connection) in bar absolute

B - Control current for A/C Compressor Regulator Valve N280 in amps

C - Permissible tolerance range (applicable to compressor capacity utilization of 10...90%)

Note. Given high ambient temperature and a low engine speed, compressor may for example no longer be able to adjust pressure on low-pressure side to value given in graph. Compressor is actuated with maximum specified control current, however delivery volume is no longer sufficient at this engine speed to reduce pressure on low-pressure side to value in graph , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar. Control current - B - is displayed in measured value block of A/C Control Head E87 or control head, Climatronic Control Module J255. Pressure in refrigerant circuit measured by High Pressure Sensor G65 or A/C Pressure/temperature Sensor G395 is displayed in measured value block of A/C Control Head E87 or control head, Climatronic Control Module J255 and --> 87 - AIR CONDITIONING . Low pressure settles as a function of control current for A/C Compressor Regulator Valve N280 within compressor output range in tolerance band. Under unfavorable conditions (very high ambient temperatures, high humidity), compressor output may not always be sufficient to attain the specified value. If compressor capacity utilization is greater than 90 %, pressure on low-pressure side may be in excess of tolerance range "C" shown in graph (compressor output no longer suffices). The specified operating current for the regulator valve must be greater than 0.3 A in order to ensure reliable valve actuation. At absolute pressure, "0 bar" corresponds to an absolute vacuum. Normal ambient pressure corresponds to "1 bar" absolute. On the scales of most pressure gauges, "0 bar" corresponds to an absolute pressure of 1 bar (can be seen from "-1 bar" mark below "0"). In "maximum cooling output" setting, control current is regulated to approx. 0.65 (vehicle-specific up to 0.85 A) (displayed in measured value block) , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. If no fault is found with this complaint, clean refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ).

Note. It is not initially necessary to clean the refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ) when this problem occurs since normally, there is only a small quantity of moisture in the system which can be removed by lengthy evacuation. If problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least 3 hours. Problem with Evaporator Vent Temperature Sensor G263 can also cause icing-up of refrigerant circuit. If this problem is encountered, also pay attention to measured value of Evaporator Vent Temperature Sensor G263 , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. Pay attention to the following as regards fault "High pressure normal, low pressure too low" : This fault may lead to icing-up of evaporator although quantity of refrigerant in circuit is OK. Check measured values of Evaporator Vent Temperature Sensor G263 and actuation of A/C Compressor Regulator Valve N280. If measured value of Evaporator Vent Temperature Sensor G263 is incorrect, evaporator may ice up or cooling output is not attained , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. Overfilling with refrigerant oil can occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil. If there is too much refrigerant oil in the circuit, the compressor must be drained and the accumulator must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ), the correct quantity of refrigerant oil is filled into the circuit --> Approved Refrigerant Oils .

Pressure Checking, Vehicles with Expansion Valve, Receiver, and A/C Compressor Regulator Valve with Externally Regulated Compressor

Note. Connecting A/C service station --> A/C Service Station, Connecting Observe test conditions --> Refrigerant Circuit, Checking Pressures with A/C Service Station . If a malfunction occurs at only one evaporator in vehicles with two evaporators, check pressures in the refrigerant circuit; if they are OK, check line connection between malfunctioning evaporator and line connection end at distribution point of refrigerant lines (for constrictions or blockage). If no malfunction can be detected, discharge refrigerant circuit and re-charge it with the specified refrigerant quantity. Then check pressures and cooling performance of A/C system again; if the malfunction occurs again, replace the expansion valve which is prematurely switched by the malfunctioning evaporator --> 87 - AIR CONDITIONING .

1. Set engine speed to 2000 RPM.
2. Observe pressure display, (e.g. pressure gauge) of A/C service station.

Note. Switching pressures for actuation of A/C Compressor Regulator Valve N280 and Coolant Fans V7 are vehicle-specific. Pressures must be measured at service connections; component locations of these connections are vehicle-specific --> 87 - AIR CONDITIONING .

Specifications

High-pressure side

Increasing from initial pressure (on connecting pressure gauges) to max. 20 bar

Low pressure

Decreasing from initial pressure (on connecting pressure gauges) to value in graph

A - Low pressure (measured at service connection) in bar absolute

B - Control current for A/C Compressor Regulator Valve N280 in amps

C - Permissible tolerance range (applicable to compressor capacity utilization of 10...90%)

Note. Given high ambient temperature and a low engine speed, compressor may for example no longer be able to adjust pressure on low-pressure side to value given in graph. Compressor is actuated with maximum specified control current, however delivery volume is no longer sufficient at this engine speed to reduce pressure on low-pressure side to value in graph , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. Under unfavorable conditions (very high ambient temperatures, high humidity), pressure on high-pressure side may increase to max. 29 bar. Control current - B - is displayed in measured value block of A/C Control Head E87 or Climatronic Control Module J255. High pressure measured by High Pressure Sensor G65 or A/C Pressure/temperature Sensor G395 is displayed in measured value block of A/C Control Head E87 or control head, Climatronic Control Module J255. Low pressure settles as a function of control current for A/C Compressor Regulator Valve N280 and control characteristic of expansion valve within compressor output range in tolerance band. Under unfavorable conditions (very high ambient temperatures, high humidity), compressor output may not always be sufficient to attain the specified value. If compressor capacity utilization is greater than 90 %, pressure on low-pressure side may be in excess of tolerance range "C" shown in graph (compressor output no longer suffices). Specified operating current for A/C Compressor Regulator Valve N280 must be greater than 0.3 A to ensure reliable valve actuation. In "maximum cooling output" setting, control current for A/C Compressor Regulator Valve N280 is regulated to approx. 0.65 A (up to 0.85 A). This measured value is vehicle-specific and displayed in measured value block. At absolute pressure, 0 bar corresponds to an absolute vacuum. Normal ambient pressure corresponds to 1 bar absolute. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of 1 bar (can be seen from -1 bar mark below 0) , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. If no fault is found with this complaint, clean refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ). Check measured values of Evaporator Vent Temperature Sensor G263 and actuation of A/C Compressor Regulator Valve N280. If measured value of Evaporator Vent Temperature Sensor G263 is not OK, evaporator may ice up or cooling output is not attained. If air conditioner operation is not OK when test is repeated after replacing expansion valve, re-install old expansion valve, clean refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ). Then replace compressor and receiver. With this fault, evaporator may ice up although quantity of refrigerant in circuit is OK. If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve N280 is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). As however refrigerant cannot flow via expansion valve, cooling output is not attained and high pressure may also not increase or only increase slightly due to the absence of energy conversion , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. If the function of the air conditioning system is not OK when the test is repeated, replace expansion valve and receiver. With this fault, evaporator may ice up although quantity of refrigerant in circuit is OK. If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve N280 is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). As however refrigerant cannot flow via expansion valve, cooling output is not attained and high pressure may also not increase or only increase slightly due to the absence of energy conversion , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING . If there is too much refrigerant oil in the circuit, the compressor must be drained and the receiver must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ), the correct quantity of refrigerant oil is filled into the circuit --> Approved Refrigerant Oils .

Note. It is not initially necessary to clean the refrigerant circuit (flush using refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ) when this problem occurs since normally there is only a small quantity of moisture in the system which can be removed by lengthy evacuation. If problem involving moisture in refrigerant circuit only occurs after a lengthy operating period or only infrequently (low pressure drops below specification and evaporator ices up), it is sufficient to replace the dryer in the receiver (adjust quantity of refrigerant oil). Refrigerant circuit is then to be evacuated for at least 3 hours. With this fault, evaporator may ice up although quantity of refrigerant in circuit is OK. Problem with Evaporator Vent Temperature Sensor G263 can also cause icing-up of refrigerant circuit. If this problem is encountered, also pay attention to measured value of Evaporator Vent Temperature Sensor G263 , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. Pay attention to the following as regards fault "High pressure normal, low pressure too low" : This fault may cause the evaporator to ice up although the amount of refrigerant in the circuit is OK. If the problem is with the A/C Compressor Regulator Valve N280 (regulator valve is not actuated but compressor operates nevertheless), refrigerant circuit does not have to be cleaned (flush with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ). In this case, it is sufficient to replace the compressor (observe quantity of refrigerant oil in compressor). If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve N280 is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). As refrigerant cannot however flow via expansion valve, cooling output is not attained and high pressure may either not increase or only slightly due to the absence of energy conversion. Check measured values of Evaporator Vent Temperature Sensor G263 and actuation of A/C Compressor Regulator Valve N280. If measured value of Evaporator Vent Temperature Sensor G263 is incorrect, evaporator may ice up or cooling output is not attained , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. This fault may also be caused by too much refrigerant oil in the circuit. Overfilling with refrigerant oil may occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil. If expansion valve is malfunctioning (permanently closed or does not open sufficiently), A/C Compressor Regulator Valve N280 is actuated to maximum output and low pressure drops to value in graph or below (compressor draws off refrigerant from low-pressure side). As however refrigerant cannot flow via expansion valve, cooling output is not attained and high pressure may also not increase or only increase slightly due to the absence of energy conversion , air conditioner Guided Fault Finding function and --> 87 - AIR CONDITIONING .

Note. Overfilling with refrigerant oil may occur if, for example, the compressor has been replaced without adjusting the quantity of refrigerant oil. If expansion valve is malfunctioning (permanently open), evaporator temperature is no longer regulated such that only refrigerant in gas form exits from the evaporator. Under certain usage conditions, liquid droplets may then be drawn in by the compressor and cause noise (liquid cannot be compressed). If there is too much refrigerant oil in the circuit, the compressor must be drained and the receiver must be replaced. After cleaning the refrigerant circuit (flushing with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ), the correct quantity of refrigerant oil is filled into the circuit --> Approved Refrigerant Oils .

Refrigerant Circuit Components, Replacing

> Leaking or Damaged Components except Compressor, Reservoir, or Receiver

> Compressor, Replacing without Flushing Refrigerant Circuit

> Compressor, Replacing Due to Leakage or Internal Damage

> Receiver or Accumulator and Restrictor, Replacing after Cleaning Refrigerant Circuit

> Receiver or Reservoir, Replacing without Flushing Refrigerant Circuit

1. All components of the refrigerant circuit submitted for quality observation are always to be sealed (use original sealing caps of replacement part).
2. To date, the replacement parts "compressor, reservoir, receiver, evaporator and condenser" have been filled with nitrogen gas. This charge is being gradually discontinued/the pressure of the nitrogen charge is now so low that escape of gas is no longer perceptible on initial opening.
3. On vehicles equipped with a compressor with no A/C clutch, the engine is only to be started following complete assembly of the refrigerant circuit (compressor always in operation as well).
4. When the refrigerant circuit is empty, the compressor with A/C Compressor Regulator Valve N280 (without A/C clutch) is switched to internal lubrication with the result that only a minimal amount of oil is pumped from the compressor into the circuit.

Note. As parts are sometimes stored for lengthy periods and at different locations within the spare parts organization, it is entirely possible that gas will escape from some parts and not from others on initial opening (even in the case of identical spare part numbers). Sealing caps at replacement part connections are therefore to be removed carefully and the nitrogen gas allowed to escape slowly. The refrigerant circuit is equipped either with a restrictor and reservoir or an expansion valve and receiver. Dryer cartridge or components with desiccant bag (reservoir, receiver) are always to be replaced after flushing refrigerant circuit; in doing so, leave sealed as long as possible to minimize absorption of moisture. Dryer cartridge or components with desiccant bag (reservoir, receiver) are always to be replaced after cleaning refrigerant circuit (flushing with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through using compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ); in doing so, leave sealed as long as possible to minimize absorption of moisture. The period of time for which a refrigerant circuit may be left open without having to replace a component with desiccant bag (reservoir, receiver) is largely governed by ambient influences. Given a high ambient temperature and a high humidity level or if the vehicle has been standing in the open for example or driven (in wet, foggy weather conditions), the period will be considerably shorter than for a vehicle which has been standing in a heated dry area. The size of the opening through which moisture may enter into the circuit also influences the period for which a refrigerant circuit can be left open without having to replace components with desiccant bag. Seal open connections and pipes (to prevent absorption of moisture). Always replace restrictor.

Refrigerant Circuit Completely Empty

Note. In the event of only a minor leak with slow escape of refrigerant (e.g. at a small leakage point), the amount of refrigerant oil lost and the amount of moisture penetrating is not sufficient to influence operation of the air conditioner. The operations marked * are only to be implemented in the case of a major leak (e.g. following an accident).

1. Remove malfunctioning component.
2. Remove compressor.*
3. Remove oil drain plug from compressor.*

Note. The oil drain plug of "Denso" and "Nippondenso" compressors is equipped with an oil seal instead of an O-ring and this is always to be replaced. To accelerate drainage of refrigerant oil, rotate compressor by way of clutch plate of A/C clutch for example. Pour old refrigerant oil out of compressor* (disposal --> Audi-ServiceNet, Handbooks, HSO Environment 2). Then fill compressor with quantity of fresh refrigerant oil corresponding to quantity of refrigerant oil in replacement compressor --> Approved Refrigerant Oils .* Use different refrigerant oils and quantities for the various compressors --> Approved Refrigerant Oils . To ensure compressor lubrication on start-up, at least 80 cm 3 of refrigerant oil must be poured into the compressor. The remainder can be added for example to the new reservoir or receiver --> Approved Refrigerant Oils . If dirt has penetrated into the compressor with the refrigerant circuit open (e.g. after an accident), compressor is to be replaced. Clean refrigerant circuit (flush with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through with compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen )*

1. Replace dryer cartridge, receiver* or reservoir* and restrictor.
2. Assemble, evacuate and recharge refrigerant circuit .

Refrigerant Circuit Contains Refrigerant

1. Discharge refrigerant circuit.
2. Remove malfunctioning component, flush with compressed air and collect escaping refrigerant oil.
3. The new component is to be filled with the amount of refrigerant oil flushed out (plus 20 cm 3 for evaporator, plus 10 cm 3 for condenser, refrigerant pipes and refrigerant hoses) as fresh refrigerant oil fill.

Note. Disposal of old refrigerant --> Audi-ServiceNet, Handbooks, HSO Environment 2

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

Compressor, Replacing Due to Leakage or Internal Damage

For example, because of noise or no compressor output

1. Discharge refrigerant circuit.
2. Remove compressor.

Note. In the event of internal damage (compressor), check refrigerant hoses and condenser. If, e.g., swarf has penetrated, clean refrigerant hoses and condenser (flush with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through using compressed air or nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ), replace refrigerant hoses if necessary. In vehicles with two evaporators, the refrigerant oil quantity in refrigerant circuit may be greater than the quantity already filled in the replacement compressor, if necessary add the remaining refrigerant oil quantity to the refrigerant circuit --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen .

1. Replace dryer cartridge, receiver or reservoir and restrictor.
2. Examine expansion valve for dirt or corrosion and replace if necessary.
3. Assemble, evacuate and charge refrigerant circuit.

Receiver or Accumulator and Restrictor, Replacing after Cleaning Refrigerant Circuit

Note. Cleaning refrigerant circuit means flushing it with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blowing through with compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen ).

For example, on account of ingress of moisture (refrigerant circuit open for lengthy period) or contamination

1. Discharge refrigerant circuit.
2. Remove compressor.
3. Rectify cause of trouble.
4. Clean refrigerant circuit (flush with refrigerant R134a --> «Refrigerant Circuit, Flushing with Refrigerant R134a»(ref-289226-S32805393652008062700000) or blow through using compressed air and nitrogen --> «Refrigerant Circuit, Flushing with Compressed Air and Nitrogen»(ref-289226-S00981775572008062700000) ).

1. Examine expansion valve for dirt or corrosion and replace if necessary.
2. Remove oil drain plug from compressor.

Note. The oil drain plug of "Denso/Nippondenso" compressors is equipped with an oil seal instead of an O-ring and this is always to be replaced .

1. To accelerate drainage of refrigerant oil, rotate compressor by way of clutch plate of A/C clutch for example.
2. Pour old refrigerant oil out of compressor.

Note. Disposal of old refrigerant --> Audi-ServiceNet, Handbooks, HSO Environment 2

1. Then fill compressor with quantity of fresh refrigerant oil corresponding to quantity of refrigerant oil in replacement compressor (or the specified refrigerant oil quantity in vehicles with two evaporators if necessary) --> «Approved Refrigerant Oils»(ref-289226-S30013434552008062700000) .

Note. Use different refrigerant oils and quantities for the various compressors --> Approved Refrigerant Oils . To ensure compressor lubrication on start-up, at least 80 cm 3 of refrigerant oil must be poured into the compressor. The remainder can be added for example to the new reservoir or receiver --> Refrigerant R134a/Refrigerant Oil Capacities and Specifications . If dirt has penetrated into the compressor with the refrigerant circuit open (e.g. after an accident), compressor is to be replaced. In vehicles with two evaporators, the refrigerant oil quantity in refrigerant circuit may be greater than the quantity already filled in the replacement compressor, if necessary add the remaining refrigerant oil quantity to the refrigerant circuit --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen .

1. Replace receiver or reservoir and restrictor.
2. Assemble, evacuate and charge refrigerant circuit.

Distinguishing features of "Showa" and "AWG" condensers

Different manifolds

Scheme 50

A - Manifold on "Showa" condenser

B - Manifold on "AWG" condenser

Different connections to pressure switch

Scheme 51

A - Connection area on "Showa" condenser

B - Connection area on "AWG" condenser

Flat tube dimensions of condenser

Note. Production was gradually switched from calendar week 45, 1998 onwards (initially for Audi A6 with 6-cyl. diesel engine) to a condenser with smaller flat tubes. Pay attention to part no. on condenser replacement (sometimes the only distinguishing feature).

Scheme 52

Condensers - A - with flat tube dimensions - B - = 20 mm and - C - = 3.0 mm must be filled with more refrigerant than condensers - D - with flat tube dimensions - E - = 18 mm or 16 mm and - F - = 1.7 mm .

Scheme 53

Pay attention to flat tube dimensions on condenser replacement. If a condenser with different dimensions is to be installed, also replace label - A - indicating refrigerant R134a capacity or delete old capacity and enter new figure using a waterproof pen .

Approved Refrigerant Oils

> Refrigerant Oil Capacities

> Capacities for Audi A2 (8Z_) from 2001

> Capacities for Audi A3 (8L_) 1997 to 2004 and Audi TT (8N_) from 1999

> Capacities for Audi A3 (8P_) from 2004

> Capacities for Audi 80 (8A_/8C_), Audi Coupe (8B_), Audi Cabriolet (8G_)

> Capacities for Audi A4 (8D_) 1995 to 2002

> Capacities for Audi A4 (8E_) from 2001, Audi A4 Cabriolet (8H_) from 2003

> Capacities for Audi 100/Audi A6 (4A_) from 1998

> Capacities for Audi A6 (4B_) from 1998 and Audi Allroad

> Capacities for Audi A6 (4F_) from 2005

> Capacities for Audi V8 (4C_) to 1994

> Capacities for Audi A8 (4D_) 1994 to 2002

> Capacities for Audi A8 (4E_) from 2003

> Capacities for Audi Q7 (4L_) from 2006

Note. As PAG (polyalkylene glycol) oil is highly hygroscopic (attracts water), opened containers are to be immediately re-sealed so as to be airtight. PAG oil from containers which have been open for a lengthy period is no longer usable.

Note. The oils used with refrigerant R12 are not suitable for refrigerant R134a. The name of the compressor manufacturer "Nippondenso" has been changed to "Denso". The refrigerant oil developed specially and exclusively for R134a refrigerant circuits is not commercially available. Refrigerant oils specifically designed for each compressor can therefore be obtained from the replacement parts range . The use of other refrigerant oils could cause system failure, as they do not always mix and thus circulate with refrigerant R134a (for compressor lubrication). There are different refrigerant oils for "Zexel" , "Denso" and "Sanden" compressors . The refrigerant oil (G 052 300 A2) for use in refrigerant circuits with "Denso" compressors (old name "Nippondenso") is also included in the retrofit kit (part number 4A0 298 107 A) . Use is to be made for refrigerant circuits with "Zexel" or "Sanden" compressor of refrigerant oil with part no. G 052 154 A2 . For refrigerant circuits with "Zexel" compressors, use can be made of both the refrigerant oil (G 052 154 A2) and the refrigerant oil (G 052 200 A2) contained in the retrofit kit (part no. 4A0 298 107) .

Tools and Materials Available from Regional Sales Center or Importer

A/C service station (this illustration shows e.g. A/C service station V.A.G 1885).

1. The operations "testing, extraction (recycling), evacuation, flushing and charging" are to be performed in line with the relevant operating instructions.
2. The filters and dryers installed are to be replaced at the latest at the end of the period of use specified in the operating instructions and whenever the station has been drained (keep replacement filter to hand; available from equipment manufacturer, refer to operating instructions).
3. Use can also be made of A/C service stations not described here .
4. Currently available A/C service stations are equipped with a program for flushing the refrigerant circuit; the flushing equipment required for flushing is also included in delivery

Note. This A/C service station comprises the following standard components: Charging cylinder, pressure gauge set, vacuum pump, shutoff valves and charging hoses. One quick-release coupling each (for service connections on high and low-pressure side) is included in the scope of delivery of this A/C service station. Depending on version, a current vacuum display (LED) may appear after pressing the "Evacuate" button again.

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Adapter for cleaning refrigerant circuit (flush with refrigerant R134a --> Refrigerant Circuit, Flushing with Refrigerant R134a or blow through with compressed air and nitrogen --> Refrigerant Circuit, Flushing with Compressed Air and Nitrogen )

A - 5/8"-18 UNF thread for conical seal

B - Union nut (for connection with O-ring) with thread

1. M 18x1.5 V.A.G/1
2. M 20x1.5 V.A.G/2
3. M 24x1.5 V.A.G/3
4. M 28x1.5 V.A.G/4

Scheme 58

A - 5/8"-18 UNF thread for conical seal

B - Threaded connection for O-ring

1. M 18x1.5 V.A.G/5
2. M 20x1.5 V.A.G/6
3. M 24x1.5 V.A.G/7
4. M 28x1.5 V.A.G/8

Scheme 59

A - 5/8"-18 UNF thread for conical seal

B - Internal thread with valve opener

1. M 10x1.25 V.A.G/9 (for connections with valve on high-pressure side)
2. M 12x1.5 V.A.G/10 (for connections on low-pressure side)

Note. A Schrader valve is screwed into connection - A -. A valve opener must be installed in the charging hose connection. Various adapters from adapter set are also part of the adapter case for VW/Audi passenger cars VAS 6338/1

Scheme 60

A - Adapter with union nut V.A.G/1 (only for connections with small valve insert on low-pressure side)

B - Charging hose with union nut 5/8"-18 UNF (short version)

C - Adapter with service connection V.A.G/2

Note. For connections with large valve insert (standard on "Zexel" compressors, gradual change to small valve insert as of 10.94), use is to be made of adapter V.A.G/10 (remove valve from adapter V.A.G/10 or install valve opener in charging hose - B -).

Commercially Available Tools and Materials

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5/8"-18 UNF thread

Note. Use differently colored charging hoses (1800 mm long). Have valve opener and spare seals to hand. A charging hose in short version is also included in adapter case for VW/Audi passenger cars VAS 6338/1.

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Seals can also be used for charging hoses.

Note. Valve caps with spare seals are also included in adapter case for VW/Audi passenger cars VAS 6338/1.

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1. Pressure gauge set
2. Pressure hose (ID 5 mm, length 2 m)
3. Nitrogen
4. Hose fitting

Note. For connection to adapter set V.A.G 1785 with 5/8"-18 UNF thread

Scheme 66

1. High-pressure side, nominal size 16 mm
2. Low-pressure side, nominal size 13 mm
3. 2x release tool (Sharan)

Note. This quick-release coupling is included in the scope of delivery of the A/C service station.

Improvised Tools

Scheme 67

A - Charging hose 5/8" - 18 UNF (version with large ID)

B - Connection for workshop compressed-air system (always use filter)