A/C System Control And Regulation Information

For these vehicles (For example the Audi A4) there are different versions of the heating and A/C system depending on the equipment. Make sure to use the correct version and pay attention to the allocation of different components. Refer to HEATING AND A/C SYSTEM VERSIONS  and Parts Information.

If there is a fault in the heating and A/C system first read out the DTC memory of the Front A/C Display Control Head -E87- using the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function. If a message appears to check the DTC memory of a different control module, also check the DTC memory of this control module (for example, the Vehicle Electrical System Control Module -J519-, the Comfort System Central Control Module -J393-). Certain A/C system components (for example, the A/C Compressor Regulator Valve -N280-) are not directly activated by the Front A/C Display Control Head -E87- or their measured values are not directly evaluated by the Front A/C Display Control Head -E87-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function.

If no malfunction is displayed, check the affected measured values of the Front A/C Display Control Head -E87- and activate any potentially concerning component using the "output diagnostic test mode" function. Use the Vehicle Diagnostic Tester.

The "electrical test" function is not described in this service information. Perform an electrical test via the "Guided Fault Finding"  function. Information can also be found here on the functions that should be checked. Use the Vehicle Diagnostic Tester.

Certain A/C system functions can be switched on and off via the MMI (Multi Media Interface) in the "A/C system" function under the "Car" / "Vehicle" menu. The A/C system control can also be influenced via the presets in the MMI (Multi Media Interface) under the "A/C system" function in the "Car" / "Vehicle" menu. Therefore, check the preset in the MMI first in the case there is a concern with these components. Refer to Infotainment/MMI Owner's Manual.

The temperature-dependent resistance values of the various temperature sensors are recorded in tables, which can be accessed using the "Guided Fault Finding"  function on the Vehicle Diagnostic Tester.

The electrical test for the various actuators is described in Guided Fault Finding. Use the Vehicle Diagnostic Tester.

Repair work on refrigerant circuit. Refer to REFRIGERANT CIRCUIT .