Test Requirements
- Ambient temperature greater than 15 °C (59 °F).
- Radiator and condenser are clean (if necessary clean).
- The ribbed belt, which drives the A/C compressor, is OK and tensioned correctly. The belt pulley is actually driving the A/C compressor (vehicles without a high voltage system).
- All air guides, covers and seal OK and properly installed
- Seal between engine compartment, engine hood and plenum chamber is OK and installed correctly. To check. Refer to OVERVIEW - BULKHEAD / OVERVIEW - PLENUM CHAMBER COVER ; (Plenum Chamber Cover Overview).
- The air flow through the dust and pollen filter is not affected by dirt in the filter. To check. Refer to DUST AND POLLEN FILTER, REMOVING AND INSTALLING .
- The air intake for the A/C unit (in fresh-air and recirculated-air modes) is not affected by dirt or retrofitted components.
- Vehicles without glove compartment cooling: glove compartment cooling connection is sealed on the A/C unit. Refer to OVERVIEW - AIR ROUTING AND AIR DISTRIBUTION IN PASSENGER COMPARTMENT .
- Vehicles with glove compartment cooling: glove compartment cooling connection is installed on the A/C unit according to specification (not planned at this time, introduction not yet finalized). Refer to OVERVIEW - AIR ROUTING AND AIR DISTRIBUTION IN PASSENGER COMPARTMENT .
- The vehicle is not exposed to sunlight.
- Engine is warm: coolant temperature is greater than 80 °C (176 °F).
On vehicles with a high voltage system the engine does not always run when the ready mode is active. If the engine is too cold and the Hybrid Battery Unit -AX1- is charge enough that the engine does not start if necessary when the ready mode is active (display in the instrument cluster "power meter") by changing the settings in the MMI in the "e-tron mode" function in the "Car" / "Car system menu " for example on "Raising battery charge" or by releasing the hood of the vehicle allows the engine to start and run. Refer to the Owner's Manual and Infotainment/MMI Operating Instructions.
- The DTC memory for the A/C Control Module -J301- /Climatronic Control Module -J255- control head was checked and erased, basic setting performed and the A/C Control Module -J301- /Climatronic Control Module -J255- coding checked. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- A/C Control Module -J301- /Climatronic Control Module -J255- adaptation checked. Use the Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- All instrument panel vents and, if present, vents in the rear center console are opened.
- Check that the air outlet from the rear footwell vents (under the front seats) is not blocked by the floor mats or other objects.
- Engine hood closed.
On Vehicles with a High Voltage System (Hybrid Vehicles)
- The ignition is switched on and the ready mode is active (pay attention to the display in the "power meter") the engine starts or runs only when for example the Hybrid Battery Unit -AX1- is not charged enough or the hood is released. Refer to the Owner's Manual and Infotainment/MMI Operating Instructions.
- With the ignition switched on and the temperature preset "warm" on the A/C system control head, the Climatronic Control Module -J255- (shows "HI" in the display) the coolant flow through is maintained by the heater core for the A/C system via the High Temperature Circuit Coolant Pump -V467-. Refer to HIGH VOLTAGE HEATER (PTC) -Z115-, INCORPORATION, IN THE COOLANT CIRCUIT and COOLANT PUMP/COOLANT THERMOSTAT [CNSB, CNTC] / COOLANT PUMP/THERMOSTAT [CRUA, DEJA] or COOLANT PUMP/COOLANT THERMOSTAT [CNSB, CNTC] / COOLANT PUMP/THERMOSTAT [CRUA, DEJA] .
The engine may start unexpectedly when performing work while the ignition is turned on or when the ready mode is activated and may cause poisoning in enclosed spaces. Be aware of body limbs and/or clothing when clamping or pulling.
Perform the following steps before turning on the ignition:
- Move the selector lever into position P .
- Activate the parking brake.
- Switch off ignition.
- Open the engine hood.
- Connect the charging unit for example Battery Charger :VAS5095A to the battery jump start terminal for the 12V vehicle electrical system
- Switch on the ignition.
-- Switch on the ignition and activate the ready mode is active (the engine need not start).
Vehicles Without High Voltage System
-- Start the engine.
-- The engine runs (if necessary adjust the settings on the control head (the A/C Control Module -J301- or the Climatronic Control Module -J255-) in the direction "heat").
Vehicles with Manually Controlled A/C System
-- Adjust the following settings on the A/C Control Module -J301- control head:
- Turn the temperature regulator -1- to the "cold" stop.
- A/C compressor on: the indicator lamp in the AC (or A/C ) button -5- illuminates.
- Recirculated-air mode on: the indicator lamp in the recirculation button -2- illuminates.
- Turn the air distribution knob -4- to the "instrument panel vent" stop.
- Turn the fresh air blower regulator -3- to the maximum speed.
Vehicles with Automatic Climate Control System (with and without a High Voltage System)
-- Adjust the following settings on the Climatronic Control Module -J255- control head:
- "Auto" mode: the indicator lamp in the AUTO button -11- illuminates.
- Set the temperature preset "cold" via the regulators -1 and 7- : "LO" for the driver and front passenger side in the display -3- on the Climatronic Control Module -J255-.
- A/C compressor on: the indicator lamp in the AC (or A/C ) button -8- illuminates.
- Turn the fresh air blower regulator -9- to the maximum speed.
- "eco" mode not activated: nothing appears in the display -3- on the Climatronic Control Module -J255-.
The indicator lamp in the AUTO button turns off when the fresh air blower speed is changed manually.
For all Vehicles
The maximum possible fresh air blower speed depends on several conditions (vehicle voltage, etc.)
Function with the engine running (on vehicles without a high voltage system):
Function with ready mode active (on vehicles with a high voltage system):
- Run the Coolant Fan -V7- /Coolant Fan 2 -V177-. The actuation and speed depend on the pressure in the refrigerant circuit and the engine temperature.
The Coolant Fan -V7- /Coolant Fan 2 -V177- are only switched from a certain pressure in the refrigerant circuit (from a pressure of 9 bar (130.5 psi) at this time) depending on the A/C Control Module -J301- /Climatronic Control Module -J255- control head version. The coolant fan actuation is displayed in the "Read measured values" function. Use the :Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
Depending on the engine control module, the target and the actual speed of the Coolant Fan -V7- and Coolant Fan 2 -V177- can vary from one another. Use the :Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
- The fresh air blower runs at maximum speed.
The maximum possible fresh air blower speed depends on several conditions (vehicle voltage, etc.)
- The A/C system goes into recirculated-air mode. Approximately one minute after starting the engine (activating the ready mode), the back pressure/fresh air door is closed and the recirculation door is opened. The fresh air blower extracts the air from passenger compartment below instrument panel/behind the glove compartment.
If one of these prerequisites is not met:
-- Check the DTC memory, perform an output diagnostic test and read the measured values. Use the :Vehicle Diagnostic Tester in the"Guided Fault Finding" function.
Continuation
Refer to COOLING OUTPUT, CHECKING
Refer to COOLING OUTPUT, CHECKING
Refer to COOLING OUTPUT, CHECKING, VEHICLES WITH AUTOMATIC CLIMATE CONTROL SYSTEM (WITH HIGH VOLTAGE SYSTEM)