Air Conditioning: Diagnosis Audi Q7 4L facelift

COMPONENTS ACTUATED BY A/C SYSTEM, ELECTRICAL TEST

Note. Various electrical components of the vehicle (e.g. Heated Rear Window -Z1- and heated seats) which do not belong to the A/C system are actuated by the front Climatronic Control Module -J255- (or the Rear A/C Display Control Head -E265-). Perform an electrical test as described in Guided Fault Finding. Refer to Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".

TEST REQUIREMENTS

Special tools and workshop equipment required

1. Diagnostic Operation System VAS 5051 A (or Vehicle Diagnosis & Service System VAS 5052)
2. On vehicles with Basic version A/C system, a conventional thermometer (for measuring temperature, if necessary use a thermometer with 2 measuring probes for simultaneous measurement e.g. temperature on right and left sides).

Note. On vehicles with Comfort version A/C system, the specified temperatures themselves can be measured or read out via the "Read measuring value block" function using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding". On vehicles with a rear heating & A/C unit, cooling performance in front heating & A/C unit must be checked first. only when this is OK can the cooling performance of rear heating & A/C unit can be checked REAR A/C SYSTEM, TESTING COOLING PERFORMANCE .

Test Requirements

1. Ambient temperature greater than 15 °C.
2. Radiator and condenser are clean (if necessary clean).
3. Compressor drive ribbed belt is OK and correctly tensioned and belt pulley actually drives the compressor (on 6 cylinder TDI engine), refer to «COMPRESSOR, REMOVING AND INSTALLING ON BRACKET»(ref-491706-S32459619332012073100000) .
4. Compressor drive unit is mounted correctly, compressor is actually driven (on 8 cylinder FSI engine), refer to «COMPRESSOR»(ref-491706-S23648515632012073100000) .
5. All air ducts, covers and seals are OK and properly installed.
6. Air flow through dust and pollen filter is not impaired by soiling (removing and installing dust and pollen filter, refer to «DUST AND POLLEN FILTER»(ref-491706-S11857566202012073100000) ).
7. Vehicle not exposed to sunlight.
8. Engine is warm.
9. DTC memory of Climatronic Control Module -J255- (and of Rear A/C Display Control Head -E265-) has been checked and erased, basic setting has been performed using Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function.
10. Coding of Climatronic control module has been checked using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
11. Adaptation of Climatronic control module (and of rear A/C display control head) was checked using Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault.
12. All vents (of instrument panel, in rear center console and in B and C pillars) have been opened. (for vehicles with rear A/C system).
13. All instrument panel vents open (On vehicles with Comfort version A/C system without rear A/C system, vents in rear center console and in B pillars closed).
14. The hood is closed.
15. The following are set on Climatronic control module or on MMI (Multi Media Interface) (Refer to Owner's Manual and Owner's Manual / Infotainment/MMI)

Auto operating mode (on Comfort version A/C system)

Temperature preselect LO (for driver's and front passenger's side on Comfort version A/C system) or temperature rotary actuator at cold stop (for Basic version A/C system)

Compressor switched on (function Econ is not active).

Rotary switch for fresh air blower speed in position 4 (on Basic version A/C system)

1. Settings on rear A/C display control head (if present, optional equipment)

Operating mode Auto for air distribution.

Temperature preselect LO (for left and right sides).

1. Functions with engine running

Coolant Fan -V7- is running or is switched on when a certain pressure in refrigerant circuit is exceeded (speed depends on pressure in refrigerant circuit and on engine coolant temperature).

Note. At this time, Coolant Fan always operates while compressor is switched on, however it may be in the future that it is switched on only during cooling performance testing as soon as a certain pressure in refrigerant circuit is exceeded, depending on version of Climatronic control module (activation of Coolant Fan is displayed in the measuring value block of Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function).

Fresh Air Blower -V2- runs at maximum speed.

Front A/C system switches to air recirculation mode (fresh air intake is closed approximately 1 minute after starting vehicle) and air is drawn in from front passenger's footwell (by Fresh Air Blower).

Note. At this setting (maximum cooling output), Coolant Pump -V50- is not actuated by the Climatronic Control Module. However it may be switched on by the respective Engine Control Module (ECM), depending on engine and on the current coolant temperature. At this time, the Coolant Pump is not installed on vehicles with 6 cylinder gasoline engine without parking heater optional equipment. On these vehicles, Coolant Pump -V36- is installed to circulate the coolant. Coolant Pump -V36- may also run if A/C system does not require heat output (e.g. at setting for maximum cooling output), it may then be actuated by ECM depending on the coolant temperature.

If one of these test requirements is not fulfilled, check the DTC memory for the Climatronic control module, perform output diagnostic test mode and read the measured value block using vehicle diagnosis, testing and information system VAS5051 in the "Guided Fault Finding" function.

REAR A/C SYSTEM, TESTING COOLING PERFORMANCE

Special tools and workshop equipment required

1. Diagnostic operation system VAS 5051 A (or Vehicle Diagnosis & Service System VAS 5052)
2. On vehicles with Basic version A/C system, a conventional thermometer (for measuring temperature, if necessary use a thermometer with 2 measuring probes for simultaneous measurement e.g. temperature on right and left sides)

Note. On vehicles with Comfort version A/C system, the specified temperatures themselves can be measured or read out via the "Read measuring value block" function using. Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding". On vehicles with a rear heating & A/C unit, cooling performance in front heating & A/C unit must be checked first TEST REQUIREMENTS , only when this is OK can the cooling performance of rear heating & A/C unit can be checked REAR A/C SYSTEM, TESTING COOLING PERFORMANCE .

Note. If there is a complaint at only the evaporator in rear heating & A/C unit on vehicles with two evaporators, first perform cooling performance testing at front A/C system TEST REQUIREMENTS . If cooling performance at front is OK, check cooling performance at rear A/C system. If, during cooling performance testing on rear A/C system, it is detected that performance is not sufficient and then no cause for the complaint can be found, check line connection between evaporator in question and exit of line connection at distribution point of refrigerant lines in left front wheel housing (e.g. for constriction). If the fault cannot be found, bring vehicle to a workshop that has the necessary tools and in which the work can be performed accordingly by qualified personnel. Refer to General Information . There is no sensor that measures air temperature downstream of evaporator installed in rear heating & A/C unit, compressor performance control is performed therefore only via the measured value of Evaporator Vent Temperature Sensor -G263- which is installed in front heating & A/C unit. Under certain unfavorable conditions, it may occur therefore because of this that the temperature set on the rear heating & A/C unit is not attained during normal regulated operation even though the A/C system is OK. Also it may occur that e.g. on an A/C system on which the specified outflow temperature has already been attained in the front heating & A/C unit and maximum cooling output is requested at rear A/C system, the rear outflow temperature is a few degrees °C higher than when a high cooling output is requested at front A/C system (if necessary increase front cooling output via setting at front).

1. Test Prerequisites, refer to «REAR A/C SYSTEM, TESTING COOLING PERFORMANCE»(ref-491706-S19980190042012073100000) .
2. Rear Cooling Output, checking, refer to «REAR A/C SYSTEM, TESTING COOLING PERFORMANCE»(ref-491706-S19980190042012073100000) .

Test Prerequisites

1. Cooling performance of front A/C system was checked and is OK «TEST REQUIREMENTS»(ref-491706-S41535249672012073100000) .
2. Test requirements for testing front cooling performance are met «TEST REQUIREMENTS»(ref-491706-S41535249672012073100000) .
3. Air intake for Rear Fresh Air Blower -V80- via the air intake grille installed in left luggage compartment lining is not obstructed by objects, refer to «AIR DUCT IN REAR HEATING & A/C UNIT»(ref-491706-S03936137792012073100000) .

Rear Cooling Output, Checking

Perform test of front cooling performance, refer to A/C SYSTEM COOLING PERFORMANCE, CHECKING .

Note. Measured values of temperature sensors (Left Rear Vent Temperature Sensor -G405- and Right Rear Vent Temperature Sensor -G406-) installed in air duct are evaluated for cooling performance test of rear A/C system. By using these measured values, it is then not necessary to remove components for the test. For the cooling performance test at front and rear, the same settings on Climatronic Control Module -J255- and on Rear A/C Display Control Head -E265- are required (Auto operating mode, temperature preselect Lo).

Initiate On Board Diagnostic (OBD) for rear A/C display control head of A/C system using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

In the rear A/C display control head select "read measured values block" the display group with the measured values from the Left Rear Vent Temperature Sensor -G405- and Right Rear Vent Temperature Sensor -G406- using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding".

Compare the displayed value (of the left rear vent temperature sensor and right rear vent temperature sensor) with the values in the diagram.

A - Vent temperature on the evaporator, depending on the outside air temperature (measured air temperature on left rear vent temperature sensor and right rear vent temperature sensor)

B - Ambient temperature

C - Permissible tolerance range

The air temperature measured by left rear vent temperature sensor and right rear vent temperature sensor must be the same or a maximum of 5 °C higher after 5 minutes than the specified vent temperature at evaporator, depending on ambient temperature (see diagram).

Note. If the A/C system is OK and the same temperature is reached on both evaporators (inside the front and rear A/C), then the temperature on the front evaporator is displayed in the measured values block for the Climatronic control module (measured value from the Evaporator Vent Temperature Sensor -G263-). The air travelling from evaporator to vents is heated slightly by heat radiated by heater core in heating & A/C unit and by leaking air which flows by at temperature doors through the heater core.

If the required values are not reached in either display fields, then check the measured values from the left rear vent temperature sensor and right rear vent temperature sensor and the activation of the Right Rear Temperature Door Motor -V314- and Left Rear Temperature Door Motor -V313- using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding". If the fault cannot be found, bring vehicle to a workshop that has the necessary tools and in which the work can be performed accordingly by qualified personnel (there is a fault in the refrigerant circuit). Refer to General Information .

If the values required are obtained only on one side, check measured value of sensor, Left Rear Vent Temperature Sensor -G405- or Right Rear Vent Temperature Sensor -G406-, which has the measured value not in the permissible range. If measured value is OK, check function of control motor and temperature door operation for the side where the measured value is not OK (Right Rear Temperature door Motor, refer to RIGHT REAR TEMPERATURE DOOR MOTOR -V314 or Left Rear Temperature door Motor, refer to LEFT REAR TEMPERATURE DOOR MOTOR -V313 ) using Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function. If no malfunctions can be determined here, check air duct in rear heating & A/C unit, refer to AIR DUCT IN REAR HEATING & A/C UNIT .