A/C System Control and Regulation Components Outside Passenger Compartment

A/C System Control and Regulation Components Outside Passenger Compartment

All Vehicles

• If there is a malfunction in the A/C system, first check the memory of the A/C Control Head Climatronic Control Module (J255) heater control head DTC memory Vehicle Diagnostic Tester in "Guided Fault Finding" function. If a different control unit displays a message to read the DTC memory, read the DTC memory on this control unit (for example, the vehicle electrical system control module (J519) , the Comfort System Central Control Module (J393) ); certain components of the A/C system (for example, the compressor regulator valve (N280) , the A/C Pressure/Temperature Sensor (G395) ) are no longer activated directly by the Climatronic control module display and control head and their measuring values are no longer evaluated directly by the Climatronic control module.

• If no fault is displayed, then read the measured value block for the Climatronic control module, and test the component using the "control diagnosis" of the Vehicle Diagnostic Tester in "Guided Fault Finding" function

• The function "electrical testing" is not described in this Repair Manual. Perform electrical testing via "Guided Fault Finding" function. Here notes can also be found on the functions which should be tested using the Vehicle Diagnostic Tester in "Guided Fault Finding" function.

• Temperature-dependent resistance values of the various temperature sensors are stored in one table, these can be called up via the "Guided Fault Finding" function of the Vehicle Diagnostic Tester in "Guided Fault Finding".

• The electrical test of the different control motors is described in Guided Fault Finding using the Vehicle Diagnostic Tester in "Guided Fault Finding" function.

• Servicing operations on refrigerant circuit are described in => [ Refrigerant Circuit, Servicing ] Refrigerant Circuit, Servicing.

• Perform the following work after completion of repair operations:

- Check the Climatronic control module (J255) DTC memory and erase any displayed malfunction if necessary using the Vehicle Diagnostic Tester in "Guided Fault Finding" function.

- Coding of Climatronic Control Module A/C control head was checked using the Vehicle Diagnostic Tester in "Guided Fault Finding" function.

- Adaptation of the Climatronic Control Module was checked using the Vehicle Diagnostic Tester in "Guided Fault Finding" function.

- Perform a basic setting on the A/C system using the Vehicle Diagnostic Tester in "Guided Fault Finding" function.

• Coolant hoses from connections to A/C unit heater core, removing and installing, refer to => [ Heater Core/Housings ] Heater Core/Housings

• Depending on vehicle production period, connection points may be installed in refrigerant lines on certain versions (not planned at this time, introduction not yet finalized). Refer to Electronic Parts Catalog (ETKA). As with connections on various components, these connection points may only be loosened and opened when the refrigerant circuit is empty.

• For vehicles with 6 cylinders and other engines with certain optional equipment (such as vehicles with the Start/Stop system) but without an "auxiliary heater" have a coolant pump (V50) (a water pump (V36) ). Refer to => [ Coolant Pump ] Coolant Pump.

• Depending on the version of the Climatronic control module (J255) A/C control head, coolant pump (V50) may be referred to as water pump (V36) in Guided Fault Finding. Refer to the Vehicle Diagnostic Tester in "Guided Fault Finding" function.

• The coolant pump (V50) ( water pump (V36) ) versions and activation differ depending on the version of the vehicle and production period. From MY 12 beginning with start of production, pumps that were controlled by a 500 Hertz signal (500 pulses per second) are being replaced by pumps that are controlled by a 100 Hertz signal depending on the engine. Pumps, controlled by a 100 Hertz signal, also have a diagnostic function and are controlled by the engine control module. Check for the correct allocation; refer to the Vehicle Diagnostic Tester in "Guided Fault Finding" function, and to the Electronic Parts Catalog.

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