Control Assembly: Description and Operation
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. Refer to => [ Refrigerant Circuit, Servicing ] Refrigerant Circuit, Servicing
• 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.
Hybrid Vehicles
Read and follow all of the supplemental warnings for all work performed on vehicles with the high voltage system.
Risk of unintended engine start
The ignition must be turned off and the ignition key must remain outside of the vehicle when working on vehicles with a high voltage system.
How to handle high voltage cable:
• Do not stand on or place tools on high voltage cables and their components as it may damage the cable insulation.
• Never bend or kink high voltage cables forcefully as it may damage the cable insulation.
• Color-code the round high voltage connector with an external color ring and code them mechanically using the guide- or code tabs. Always make certain that the coding matches when connecting the round connector in order to avoid mechanically damaging the high voltage connector.
There is a risk of electrocution from damaged high voltage components
Observe the following when working around high voltage components and high voltage wires:
• Never work around high voltage components and cables with cutting, deformed, or sharp edged tools, or heat sources such as welding or soldering tools, heated air, and thermal glue.
• Inspect the high voltage components visually before beginning.
• Perform a visual inspection of the electric drive power and control electronics (JX1) , the electro-drive drive motor (V141) , the A/C compressor (V470) and the high voltage lines when working in the engine compartment.
• Perform a visual inspection of the high voltage lines and the cover when working on the underbody.
• Perform a visual inspection of the high voltage lines and the Electrobox with the high voltage system maintenance connector (TW) when working in the luggage compartment.
• Perform a visual inspection on all of the potential equalization cables.
Observe the following items when performing the visual inspection:
• The components do not display any signs of external damage.
• The high voltage cable insulation and the potential equalization cables are not damaged.
• The high voltage cables do not display any abnormal deformations.
• Every high voltage component is marked with a red warning label.
• Components for vehicles with or without a high voltage system which are the same. Refer to => [ Components Outside of Vehicle Interior (All Vehicles) ] Components Outside of Vehicle Interior (All Vehicles).