Air Door: Testing and Inspection
General Information
Special tools, testers and auxiliary items required
• Battery charger, 60A (VAS 5903)
• A standard thermometer (for temperature measurements, if necessary a thermometer with 2 measuring probes for simultaneous measurement e.g. for temperature on the right and left)
With high voltage systems (hybrid vehicles)
If it is necessary for the following procedure to perform work in the vicinity of high voltage components, perform a visual inspection of the high voltage components and cables for damages, refer to => [ Visual Inspection of High-Voltage Components and Cables for Damage ] Visual Inspection of High-Voltage Components and Cables For Damage and always follow the warnings when working on 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.
Working on a high voltage system when activated or with the ignition turned on
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, such as (VAS 5093) to the battery jump start terminal for the 12V vehicle electrical system
• Switch on the ignition
- Charge the vehicle battery using the (VAS 5903) in the battery support mode to minimize the number of automatic starts during the test- and measuring procedures while the ready mode is active.
- Move the selector level into position "P", activate the parking brake and arrange the necessary tools for testing and measuring procedures that require the ready mode to be active or that require the ignition to be on, so that they cannot come into contact with the turning components in the engine and so that they are not in the vicinity of the turning components of a running engine.
• Also move the selector lever into position "P" and activate the parking brake for testing and measuring procedures which require the ignition to be on, but do not require the ready mode to be active.
• The ready mode is displayed in the instrument cluster control module (J285) above the "power meter". Refer to the Owner's Manual.
• Activate and deactivate the ready mode. Refer to the Owner's Manual (consult the display in the instrument cluster control module).
• If the ignition is turned on and the ready mode is active, the engine runs or starts only, when heated coolant is necessary to reach the temperature setting in the vehicle interior or for example the traction battery (A2) (hybrid battery) has not been charged enough.
• The coolant flow through is maintained by the heater core for the A/C system via the coolant pump (V50) when the ignition is turned on and the drive ready mode is active (the engine is not running). The activation of the coolant recirculation pump occurs, depending on the version of the vehicle, directly from the Climatronic control module (J255) or at the request of the Climatronic control module from the corresponding engine control module.
- Activate the ready mode (observe the display in the instrument cluster control module (J285) ). Refer to the Owner's Manual.
All vehicles
If coolant circuit is not completely bled after filling, air may accumulate in heater core of A/C unit, thus reducing heating performance of A/C system, additional noises may occur or customer may complain of different air temperatures flowing out of vents at driver's side and front passenger's side at the same setting.
Corrective action:
- Perform a longer road test at a higher engine RPM with the setting "A/C system maximum heating output" (at least for 10 minutes, engine RPM higher than 2,500). Select a low gear during the test to prevent excessive vehicle speed.
- If customer complains of poor heating performance at specific engine speeds, check incorporation of heater core in A/C system in the coolant circuit. If both coolant hoses (supply and return) of engine are interchanged, coolant is flowing in the wrong direction through the heater core.
If a different air temperature is coming out of the vents during A/C system control mode, it may be caused by the following.
• One or more of the temperature doors in the heater core housing do not close completely or do not reach their end position.
• There is air in the heater core (fluctuating flow through heater core and heat is not distributed uniformly).
• A foam seal has loosened during installation of heater core and air may flow past at heater core. Refer to => [ Heater Core/Housings ] Heater Core/Housings.
• If, when installing the auxiliary air heater heating element (Z35) / honey comb, a foam seal has come loose, air can flow out where the seal has separated. Refer to => [ Auxiliary Air Heater Heating Element (Z35)/Honey Comb ] Service and Repair.
• The A/C system refrigerant circuit is not filled with the correct quantity of refrigerant (perform a cooling performance test). Refer to => [ A/C Cooling Output, Checking ] A/C Cooling Output, Checking.
• From MY 2010, this vehicle has a Start/Stop System for specific engines as optional equipment. The setting on the Climatronic control module (J255) can prevent the Stop function. If, for example, "defrost" is selected, the stop function is not possible or will be interrupted and the engine will start. The same applies in the case of heating and cooling. The difference between the selected and actual temperature is greater than a specified value. Refer to the Vehicle diagnostic tester in "Guided Fault Finding".
• Vehicles with the Start/Stop System have an additional coolant pump (V50) ( water pump (V36) ) for the start/stop function, refer to => [ Coolant Pump ] Coolant Pump
• The coolant pump (water pump ) is controlled not only when the "Start/Stop System" is on, but also when the engine is running and when the temperature is set to "warm" on the Climatronic control module ("HI" appears in the display on the A/C control head and in the MMI). The coolant pump (water pump is activated to support the engine coolant pump. Refer to the Vehicle diagnostic tester in "Guided Fault Finding".
• The coolant pump (water pump) 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", to the and to the Parts Catalog.
The actuation of the temperature doors differs between the "Basis" A/C system and the "Comfort" A/C system Refer to => [ Heater Core Housing Temperature Doors ] Heater Core Housing Temperature Doors
- On the "Comfort" A/C system, the right font temperature door is actuated by the Right Temperature door Motor (V159) and left front temperature door by the Left Temperature door Motor (V158). Both temperature doors for the rear right footwell vent and the rear left footwell vent, as well as the vent in the rear center console are connected by a connector rod; they are actuated by the Rear Temperature door Motor (V137)
- On the "Basis" A/C system, the upper and lower temperature flaps (for the front right vents and the right footwell vents) as well as the upper and lower temperature flaps (for the front left vents and the left footwell vents) are connected to each other by the shafts. The right and left temperature door shafts are connected to each other by a connector rod; they are both actuated by the Temperature Regulator door Motor (V68).
• Heating output and temperature door activation, testing requirements, refer to => [ Heating Output and Temperature Door Activation, Testing Requirements ] Heating Output and Temperature Door Activation, Testing Requirements.
• Heat output and temperature door activation, checking, refer to Basis => [ Heating Output and Temperature Door Activation, Checking, Basis ] Heating Output and Temperature Door Activation, Checking, Basis or Comfort => [ Heat Output and Temperature Door Activation, Checking, Comfort ] Heat Output and Temperature Door Activation, Checking, Comfort.