Heating And A/C System Control And Regulation 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 no longer activated directly by the Front A/C Display Control Head -E87- or their measured values are no longer evaluated directly by the Front A/C Display Control Head -E87-.

If no malfunction is displayed, check the affected measured values of the Front A/C Display Control Head -E87- (and the Rear A/C Display Control Head -E265-) and activate any potentially problematic component using the "output diagnostic test mode" function. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function.

The "electrical test" function is not described in this service information. Perform the electrical test using the "Guided Fault Finding"  function. This also contains information regarding the functions to be tested. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding"  function.

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 .

For additional information about the components outside of the vehicle interior. Refer to COMPONENTS OUTSIDE VEHICLE INTERIOR .