Test Requirements
The following are the test requirements for a vehicle with a mechanically driven A/C compressor as an example. On vehicles with a high-voltage system (for example Audi A3 e-tron, Audi Q7 e-tron etc.) and / or the additional A/C functions (for example Audi Q7 e-tron) this arrangement varies. For these vehicles, pay attention to the specifications in the respective service information and Guided Fault Finding. Refer to COOLING OUTPUT, CHECKING (vehicle-specific service information) and use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- Radiator and condenser are clean (clean if necessary).
- The thermal insulation at expansion valve is OK and properly installed.*
- Ribbed belt is OK and properly tensioned. Ribbed belt for A/C compressor and generator are OK and correctly tensioned.*
- All air ducts, covers and seals are OK and properly installed.
- Fault finding on the electrical equipment and vacuum system found no malfunction.* Use the Vehicle Diagnostic Tester("OBD" function or "Guided Fault Finding" for the A/C system) and refer to Refrigerant Circuit (vehicle-specific service information).
- The A/C system OBD does not detect any malfunctions (when the engine is running and the A/C system is switched on), and no compressor shut-off condition is displayed in the measured value block (only for vehicles with "A/C system" OBD). Use the Vehicle Diagnostic Tester("OBD" function or "Guided Fault Finding" for the A/C system) and refer to Refrigerant Circuit (vehicle-specific service information).
- The various pressure/temperature sensors installed on or in the refrigerant circuit provide valid measured values when the A/C system is being used. To check, use the in the "Guided Fault Finding" function and refer to Component Location Overview - A/C System . If no errors can be detected, evacuate the refrigerant.
- Air flow through dust and pollen filter not obstructed by dirt*
- The A/C 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*
- Air guide doors in the A/C unit, heater and evaporator reach their end position*
- Fresh-air intake ducts beneath hood and in passenger compartment as well as corresponding water drain valves OK*. Refer to Air Routing (vehicle-specific service information).
- The engine is warm.
- Vehicle is not exposed to direct sunlight. Refer to COOLING OUTPUT, CHECKING (vehicle-specific service information).
- The ambient temperature is greater than 15 °C (59 °F).
- All instrument panel vents are open.
-- Start the engine.
Settings on the A/C system control module, for example on the Front A/C Display Control Head -E87- or the Climatronic Control Module -J255- (and Rear A/C Display Control Head -E265- for vehicles with two A/C units):
-- Preselect "Auto" mode (A/C compressor on).
-- Set temperature preset to "LO" on the driver and front passenger side (and the rear passenger compartment, left and right side in vehicles with two A/C units).
Setting on heater controls:
-- Press A/C button and rec- or recirculation button.
-- Turn temperature knob towards "cold" stop.
-- Set the fresh-air blower dial to position "4".
The following system test conditions should be met:
- One or more Radiator Fan -V7- (Radiator Fan 2 -V177-) operated (at least speed 1)*
For some versions, the fan is switched on only once the pressure in refrigerant circuit has exceeded a specified value.
- Fresh Air Blower -V2- (and Rear Fresh Air Blower -V80- in vehicles with two A/C units) running at maximum speed.
- Recirculated/fresh air door set to "Recirculated air mode" (within one minute, after starting vehicle, air-flow door is closed and recirculated-air door is opened)*
- The coolant shut-off valve is closed.*
- The valves of pump valve unit are closed and there is no coolant circulation pump delivery.*
- Compressor is actually driven (A/C Clutch -N25- operated, overload safeguard (if installed) not tripped).*
The A/C compressor is driven by different components depending on the engine (belt or input shaft). The belt pulley or the drive unit has an overload protection to protect these components and the engine, which activates if the A/C compressor runs with resistance. Refer to A/C Compressor (vehicle-specific service information).