Testing Requirements For Heating Output And Activation Of A/C System Temperature Control Doors
- The coolant circuit is bled according to the guidelines. Refer to COOLANT, DRAINING AND FILLING
- The engine is warm (the coolant temperature is higher than 80 °C (176 °F)).
- Radiator and condenser are clean (if necessary, clean).
- All air ducts, covers and seals are OK and properly installed.
- If a vehicle has electric radiator shutters, their function is OK.
- Airflow through the dust and pollen filter is not obstructed by debris. Refer to DUST AND POLLEN FILTER, REMOVING AND INSTALLING .
- The air intake for the heater and A/C unit (in fresh air and recirculating air mode) is not impaired by contamination or retrofitted components.
- Make sure that the air vent from the rear footwell vents (under the front seats) is not blocked by the floor mats or other objects.
- If equipped the air duct for glove compartment cooling is installed in the glove compartment as specified. Refer to AIR GUIDE FOR GLOVE COMPARTMENT COOLING, REMOVING AND INSTALLING .
- The vehicle is not exposed to sunlight.
- The DTC memory of the Front A/C Display Control Head -E87- is called up and erased, the basic setting is performed and the coding of the Front A/C Display Control Head -E87- is checked using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- The adaptation for the Front A/C Display Control Head -E87- was checked. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- The following is set in the MMI (Multi Media Interface) via the "A/C" function in the "Car" / "Vehicle" menu for the regulation of the A/C system: automatic recirculation "off" and "medium" footwell temperature (arrow pointing upward).
For these vehicles (For example the Audi A4) there are different versions of the A/C system depending on the equipment. Make sure to use the correct version and pay attention to the allocation of different components. Refer to HEATING AND A/C SYSTEM VERSIONS and Parts Information.
The various functions for setting the A/C system in the MMI (Multi Media Interface) ("A/C" function in the "Car" / "Vehicle" menu) differ depending on the A/C system version, the vehicle date of manufacture and the vehicle version (and may not be available for all versions). Refer to Vehicle Operating Instructions.
On USA version vehicles, certain settings for the A/C system via the MMI are no longer available from a specific date of manufacture. Refer to the Owner's Manual. Also pay attention to the coding and adaptation of the Front A/C Display Control Head -E87-. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- All instrument panel vents and, if equipped, the vents in the rear center console are opened.
- The hood is closed.
- The engine is running and the temperature is set to "warm" ("HI" display) on the Front A/C Display Control Head -E87- (and the Rear A/C Display Control Head -E265- if present) and in the MMI display.
-- The Coolant Shut-Off Valve -N82- is not activated.
-- For vehicles with a regulated coolant circuit (only installed in certain engines), the activation and function of these components are OK (for example, a regulated coolant pump). Refer to CONNECTION DIAGRAM - COOLANT HOSES .
For vehicles with an engine with a regulated coolant circuit (for example, with a regulated coolant pump and a Cylinder Head Coolant Valve -N489-), there is currently no Coolant Shut-Off Valve -N82- installed. For an engine with a regulated coolant pump, the engine control module activates the coolant pump, and in doing so regulates the coolant circulation. Refer to CONNECTION DIAGRAM - COOLANT HOSES .
-- The Heater Coolant Shut-Off Valve -N279- is not activated on vehicles with a parking heater.
-- If equipped, the Coolant Recirculation Pump -V50- is activated.
-- Depending on the engine, the Recirculation Pump -V55- is activated on vehicles with a parking heater.
If this component is activated on vehicles with a Coolant Shut-Off Valve -N82- (not installed on all vehicles) or with a Heater Coolant Shut-Off Valve -N279-, the vehicle interior is not heated. Use the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
If the Coolant Shut-Off Valve -N82- / Heater Coolant Shut-Off Valve -N279- does not open completely in the inactivated state, there may be a complaint regarding a lack of heating output.
For vehicles with "parking heater" optional equipment, the Coolant Shut-Off Valve -N82- is not installed. Depending on the engine, there may not be a Coolant Recirculation Pump -V50- installed. In these vehicles, the parking heater components assume this function (the Heater Coolant Shut-Off Valve -N279- and the Recirculation Pump -V55-). Refer to appropriate service information. .
On vehicles with "parking heater" optional equipment, the Recirculation Pump -V55- for the parking heater is activated and the Heater Coolant Shut-Off Valve -N279- is not actuated. Refer to appropriate service information. .
When testing the heating output, it is helpful to display the following measured values of the Front A/C Display Control Head -E87- :
- On vehicles with a "Low" A/C system the measured values of the following temperature sensors (Left Front Upper Body Vent Temperature Sensor -G385-, Left Footwell Vent Temperature Sensor -G261- and Evaporator Vent Temperature Sensor -G263-).
- On vehicles with a "High" A/C system the measured values of the following temperature sensor (Left Front Upper Body Vent Temperature Sensor -G385-, Right Front Upper Body Vent Temperature Sensor -G386-, Left Footwell Vent Temperature Sensor -G261-, Right Footwell Vent Temperature Sensor -G262-, Evaporator Vent Temperature Sensor -G263-, Left Rear Footwell Vent Temperature Sensor -G637- and Rear Upper Body Vent Temperature Sensor -G537-).
- The activation of the Fresh Air Blower -V2-,
- The activation of the Radiator Fan -V7- (and if equipped the Radiator Fan 2 -V177-).
- The activation of the following components (if equipped, depending on the equipment and engine type Coolant Recirculation Pump -V50- / Recirculation Pump -V55-, Coolant Shut-Off Valve -N82- /Heater Coolant Shut-Off Valve -N279-).
- The activation of the A/C Compressor Regulator Valve -N280- (compressor shut-off conditions and actual compressor current)
- The coolant temperature and the exterior temperature.
- The measured value for the High Pressure Sensor -G65- (refrigerant pressure).
For these vehicles (For example the Audi A4) there are different versions of the A/C system depending on the equipment. Make sure to use the correct version and pay attention to the allocation of different components. Refer to HEATING AND A/C SYSTEM VERSIONS and Parts Information.
On vehicles with a "High" A/C system the air temperature and amount of air that is calculated and regulated by the Front A/C Display Control Head -E87- are also influenced by the setting Rear A/C Display Control Head -E265- -A-. However, only the temperature can be adjusted on this Rear A/C Display Control Head -E265-. Refer to Rear A/C Display Control Head -E265-, REMOVING AND INSTALLING, "High" A/C SYSTEM, A4 AND A5 .
CHECKING
The following is set on the Front A/C Display Control Head -E87- -A and B- :
- "Auto" mode (indicator lamp in the AUTO button lights up).
- "Cold" temperature preset (16 °C for the "Low" A/C system).
- "Cold" temperature preset for the driver and front passenger side ("LO" is displayed for the driver and front passenger side on the "High" A/C system.
- A/C compressor is switched on and maximum cooling output is selected (the indicator lamp in the A/C MAX button lights up).
- Preset of the Fresh Air Blower -V2- "maximum speed" (show for example in display of the Fresh Air Blower -E87- -B- "4 Bar s" or higher).
For a "High" A/C system, the following is set on the Rear A/C Display Control Head -E265- :
- "Cold" temperature setting ("LO").
For these vehicles (For example the Audi A4) there are different versions of the A/C system depending on the equipment. Make sure to use the correct version and pay attention to the allocation of different components. Refer to HEATING AND A/C SYSTEM VERSIONS and Parts Information.
For vehicles with a "High" A/C system, the air temperature and amount of air that is calculated and regulated by the Front A/C Display Control Head -E87- are also influenced by the setting on the Rear A/C Display Control Head -E265-. However, only the temperature can be adjusted on this Rear A/C Display Control Head -E265-. Refer to REAR A/C DISPLAY CONTROL HEAD -E265-, REMOVING AND INSTALLING, "HIGH" A/C SYSTEM, A4 AND A5 .
-- The activation and function of the auxiliary heater is OK on vehicles with a diesel engine and on vehicles with a high-voltage system (hybrid vehicles with a gasoline or diesel engine).
The type of auxiliary heating depends on the vehicle equipment level. On vehicles with a diesel engine without the "parking heater" optional equipment an Auxiliary Heater Heating Element -Z35- is installed, on vehicles with the "parking heater" optional equipment depending on the vehicle version the Auxiliary Heater Heating Element -Z35- is not present and the parking/auxiliary heater is activated as the auxiliary heater. Refer to AUXILIARY HEATER, TESTING .
For specific vehicles with a gasoline engine can depending on the version and the market in the future an Auxiliary Heater Heating Element -Z35- can also be installed (introduction not yet finalized).
If there is a complaint regarding insufficient heating output at low exterior temperatures on vehicles with a gasoline engine and "parking heater" optional equipment, check the settings in the MMI for activating the parking heater as an auxiliary heater and the activation and function of the parking heater as an auxiliary heater. Refer to appropriate service information. (depending on the vehicle equipment).
If there is a complaint regarding insufficient heating output at low exterior temperatures in vehicles with a diesel engine, check the settings in the MMI for the auxiliary heater and the activation and function of the auxiliary heater. Refer to ELECTRICAL AUXILIARY HEATER, TESTING .
If there is a complaint regarding insufficient heating output at low exterior temperatures in vehicles with a gasoline engine, with the "parking heater" optional equipment check the settings in the MMI for the auxiliary heater and the activation and function of the auxiliary heater. Refer to ELECTRICAL AUXILIARY HEATER, TESTING .
Certain A/C system functions can be switched on and off via the MMI (Multi Media Interface) in the "A/C system" function under the "Car" / "Vehicle" menu. The A/C system control can also be influenced via the presets in the MMI (Multi Media Interface) under the "A/C system" function in the "Car" / "Vehicle" menu. Therefore, check the preset in the MMI first in the case there is a concern with these components. Refer to Infotainment/MMI Owner's Manual.
Functions With Engine Running:
For vehicles with the Start/Stop System, the engine may only run if an additional heating output is needed to reach the selected temperature.
-- The radiator fan(s) (Radiator Fan -V7- and Radiator Fan 2 -V177-) run (activation and speed depend on refrigerant circuit pressure and engine temperature).
Depending on the version of the Front A/C Display Control Head -E87-, the radiator fan(s) (Radiator Fan -V7- and Radiator Fan 2 -V177-) are only switched on at a certain refrigerant circuit pressure (currently at a pressure of approximately 9 Bar). The activation of the radiator fan(s) is displayed in the "Read measured values" function of Guided Fault Finding. Use the Vehicle Diagnostic Testerin the "Guided Fault Finding" function.
-- The Fresh Air Blower -V2- runs at maximum speed.
The maximum possible fresh air blower speed depends on various ambient influences (coolant temperature, electrical system voltage, etc.)
-- The heating and A/C system switches to recirculation mode. Approximately one minute after the vehicle is started, the back pressure/fresh air door is closed and the recirculation door is opened. The Fresh Air Blower -V2- extracts the air from the passenger compartment below the instrument panel/glove compartment.
If one of these requirements are not fulfilled, check the DTC Memory, perform the output diagnostic test mode and read out the relevant measured value. Use the Vehicle Diagnostic Tester.
If The Above Mentioned Requirements Are Fulfilled:
- Heating Output and Temperature Control Door Activation, Checking. Refer to A/C SYSTEM HEATING OUTPUT AND TEMPERATURE CONTROL DOOR ACTIVATION, CHECKING .