Heating Output And Temperature Door Activation, Checking: Notes

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2018 Audi S8, 2018 Audi A8 Quattro, 2017 Audi S8, 2017 Audi A8 Quattro, and 2016 Audi S8. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

There is currently no Air Conditioning (A/C) system with a rear A/C unit available for vehicles with a high voltage system.

-- Close the engine hood.

-- Close the doors, the engine hood, the windows, the sunroof and the rear lid.

-- Open all instrument panel vents and the vents in the rear center console.

-- Open the vent in the left and right B-pillars.

-- Close the vent for glove compartment cooling (in the glove compartment).

-- Turn on the ignition and activate the ready mode. The engine starts automatically as needed (on vehicles with a high voltage system).

-- Start the engine (not on vehicles with a high voltage system).

Set the following on the front A/C display control head, the Climatronic Control Module -J255- :

NOTE:

By pressing the SYNC button on the Climatronic Control Module -J255-, the settings for the front driver side are applied to the front passenger side and also on the Rear A/C Display Control Head -E265- if present.

Press the SYNC button on the Climatronic Control Module -J255-.
Select "Auto" mode for the driver and front passenger side (the indicator lamps in the AUTO buttons illuminate).
Temperature preset for the driver and front passenger side set to "cold" ("LO" in the Climatronic Control Module -J255- display and control head or in the MMI display).
A/C compressor is turned on (the indicator lamp in the AC or A/C button turns on).
For the fresh air blower (front and rear), preselect "maximum speed" (shown in the display of the Climatronic Control Module -J255- and of the MMI, speed "10" or higher).
Set the air flow direction via the dials on the Climatronic Control Module -J255- for the driver and front passenger side to "footwell" and "instrument panel vents" (shown in the display of the Climatronic Control Module -J255- and of the MMI).

Set the following on the Rear A/C Display Control Head -E265- if present:

"Auto" mode (the indicator lamps in one or both AUTO buttons illuminate).
Temperature preselection "cold" (display "LO" for the left and right sides).
Preselection for the Rear Fresh Air Blower -V80- "maximum speed".
Set the air flow direction via the dials on the Rear A/C Display Control Head -E265- for the left and right side to "footwell" and "B-pillar vents" (shown in the display of the Rear A/C Display Control Head -E265-).

NOTE:

The indicator lamps in the AUTO -buttons turn off when performing manual changes for the airflow direction and/or the fresh air blower speed.

The maximum possible fresh air blower speed depends on several conditions (coolant temperature, vehicle voltage, etc.)

The instrument panel vents, the B-pillar vents, and the vents in the rear center console are open.

For vehicles on which there is also a Rear A/C Display Control Head -E265- installed for the version with the rear air distribution housing (for example on the Audi A8 hybrid and from MY 2013 for certain markets). The air temperature and volume calculated and regulated by the Climatronic Control Module -J255- is also influenced by the setting on the Rear A/C Display Control Head -E265-. However, the temperature only is adjustable for the Rear A/C Display Control Head -E265- and there is only an AUTO button, refer to REAR A/C DISPLAY CONTROL HEAD -E265-, REMOVING AND INSTALLING .

-- Initiate Guided Fault Finding of the front A/C system and select the read "measured values" function, refer to Vehicle Diagnostic Tester.

-- Let the A/C run a few minutes with maximum cooling output (A/C compressor is switched on, indicator lamp in the AC or A/C button comes on).

-- Compare the measured value of the Evaporator Vent Temperature Sensor -G263- with the measured value of the Left Vent Temperature Sensor -G150-, the Right Vent Temperature Sensor -G151-, the Left Footwell Vent Temperature Sensor -G261-, the Right Footwell Vent Temperature Sensor -G262- (and the -G639-).

NOTE:

The Rear Intake Air Temperature Sensor -G639- is only installed in vehicles with a rear air distributor housing (without a Rear A/C Display Control Head -E265- and without a rear A/C unit).

Specified Values:

Read the measured values of the heat exchanger temperature sensor Left Vent Temperature Sensor -G150-, Right Vent Temperature Sensor -G151-, Left Footwell Vent Temperature Sensor -G261-, Right Footwell Vent Temperature Sensor -G262- (and the Rear Intake Air Temperature Sensor -G639-) may be a maximum of 9 °C (48.2 °F) greater than the value of the Evaporator Vent Temperature Sensor -G263-.

NOTE:

As a result of the design of the A/C unit and the air duct in the vehicle, a certain increase in air temperature always occurs.

If the required values are not reached, perform a fault finding at a temperature increase on the evaporator, refer to Fault finding in the case of a temperature increase downstream from the evaporator (in the front A/C unit). .

NOTE:

If the measured value in one or two temperature sensors deviates from the measured values of the other temperature sensors, check this temperature sensor and the control motor which activates the temperature door upstream from this temperature sensor, refer to Vehicle Diagnostic Tester in the "Guided Fault Finding " Function.

Then additionally for vehicles with an A/C unit (and a Rear A/C Display Control Head -E265-).

-- Initiate Guided Fault Finding of the rear A/C system and select the "read measured values" function, refer to Vehicle Diagnostic Tester in the "Guided Fault Finding " function.

-- Compare the measured value of the Evaporator Vent Temperature Sensor -G263- with the measured value of the Left Rear Upper Body Vent Temperature Sensor -G635-, the Right Rear Upper Body Vent Temperature Sensor -G636-, the Left Rear Footwell Vent Temperature Sensor -G637- and the Right Rear Footwell Vent Temperature Sensor -G638-.

Specified Values:

The displayed measured values may be a maximum of 10 °C (50 °F) greater than the displayed measured value of the Evaporator Vent Temperature Sensor -G263-.

If the required values are not reached, refer to MALFUNCTION DETERMINATION IF COOLING OUTPUT OF FRONT A/C SYSTEM IS OK BUT REQUIRED VALUES NOT ACHIEVED IN REAR, VEHICLES WITHOUT A HIGH VOLTAGE SYSTEM .

-- Using the rotary switch on the front A/C display control head, the Climatronic Control Module -J255-, set the temperature setting for the driver side to "warm" (display "HI" in the display of the Climatronic Control Module -J255- and the Rear A/C Display Control Head -E265- if present).

NOTE:

If the selected temperature for the driver side on the Climatronic Control Module -J255- is not applied to all vents, press the SYNC button on the Climatronic Control Module -J255-.

The display for the preselected temperature changes for all vents (the driver and front passenger side, for the left and right rear) from "LO" to "HI".

-- Initiate "Guided Fault Finding " of the front A/C system and select the "read measured values" function, refer to Vehicle Diagnostic Tester in the "Guided Fault Finding " function.

-- Read the displayed measured values in the function "read the measured values" in the Climatronic Control Module -J255- "Guided Fault Finding " for the various temperature sensors Left Vent Temperature Sensor -G150-, Right Vent Temperature Sensor -G151-, Left Footwell Vent Temperature Sensor -G261-, Right Footwell Vent Temperature Sensor -G262- (and the -G639-), refer to Vehicle Diagnostic Tester.

NOTE:

The Rear Intake Air Temperature Sensor -G639- is only present in vehicles without a Rear A/C Display Control Head -E265-.

Specified Values:

The measured temperature for all temperature sensors increases to above 50 °C (122 °F) (depending on the engine temperature at the time).

NOTE:

Decrease the speed of the Fresh Air Blower -V2- and the Rear Fresh Air Blower -V80- for vehicles with a high voltage system if necessary. The delivery for the Coolant Recirculation Pump -V50- is not always sufficient enough to reach the required heating output, when the engine is idle and the maximum fresh air blowing speed is set.

The Coolant Recirculation Pump -V50- maintains the refrigerant flow through the heater core heater in the A/C system when the engine is not running for vehicles with a start-stop system and for vehicles with a high voltage system.

The Coolant Recirculation Pump -V50- can be installed in different locations. It is installed in the plenum chamber for most vehicles. For vehicles with a high voltage system (hybrid vehicles) it is located between the plenum chamber bulkhead and the engine.

The activation of the Coolant Recirculation Pump -V50- varies. For most vehicles, the Climatronic Control Module -J255- is activated directly by the front Climatronic control module A/C display and control head. For vehicles with the high voltage system (hybrid vehicles) the activation is carried out according to the requirements of the Climatronic Control Module -J255- via the respective Engine Control Module (ECM), refer to Wiring Diagram.

The required values are achieved at all temperature sensors:

Continuation of the test in vehicles without a rear A/C unit (with and without a Rear A/C Display Control Head -E265-), refer to, CONTINUATION OF THE HEATING OUTPUT TEST OF THE FRONT AND REAR A/C UNITS (CHECK THE SEPARATION FOR THE TEMPERATURE CONTROL BETWEEN THE LEFT AND RIGHT SIDE IN THE A/C UNIT). (check the separation for the temperature control between the left and right side in the front and rear A/C unit).
Continuation of the test in vehicles with a rear A/C unit (and a Rear A/C Display Control Head -E265-), refer to CONTINUATION OF THE TEST OF THE HEATING OUTPUT AND THE ACTIVATION OF THE TEMPERATURE DOORS IN A VEHICLE WITH A REAR A/C UNIT (check the heating output of the rear A/C unit).

NOTE:

At the start of production, a Rear A/C Display Control Head -E265- was installed only on vehicles with a rear A/C unit. A different version of the Rear A/C Display Control Head -E265- is installed on the Audi A8 hybrid without a rear A/C unit (with rear air distribution housing). This version of the Rear A/C Display Control Head -E265- may be installed, depending on the version of the vehicle from MY 2013, the country variant and also on other vehicles without a rear A/C unit, refer to REAR A/C DISPLAY CONTROL HEAD -E265-, REMOVING AND INSTALLING .

If the required values are not reached on any of the temperature sensors:

Check the activation and function of the Coolant Recirculation Pump -V50- (of the Recirculation Pump -V55-) and of the Coolant Shut-Off Valve -N82- (of the Heater Coolant Shut-Off Valve -N279-) Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
Check the incorporation of the A/C system into the coolant circuit, refer to INCORPORATION OF A/C SYSTEM INTO COOLANT CIRCUIT .
Check the coolant circuit bleeding, refer to the appropriate service information .
Check the heating output of the A/C system at an engine speed of approximately 1500 to 2000 RPM (repeat the test at a higher engine speed). If the required heating output is not reached at this engine speed, the fault is not in the A/C unit but rather in the coolant circuit (incorporation of the A/C system into the coolant circuit, engine coolant pump delivery, the coolant flowing through the heater core in the front A/C unit, incorporation of the Coolant Recirculation Pump -V50- into the coolant circuit, etc.), refer to INCORPORATION OF A/C SYSTEM INTO COOLANT CIRCUIT and the appropriate service information .
Check that the engine coolant pump is functioning correctly (for a defective coolant pump or a Coolant Recirculation Pump -V50- insufficient coolant may be flowing through the heater core for the heater in the front and rear A/C unit), refer to OVERVIEW - COOLANT PUMP .

NOTE:

On vehicles with an engine with a regulated coolant circuit (for example, with a regulated coolant pump and a Cylinder Head Coolant Valve -N489-), no coolant shut-off valve -N82- is currently being installed. On an engine with a regulated coolant pump, the ECM activates the coolant pump, and in doing so regulates the coolant circulation.

If the required values are not reached at only one or two temperature sensors:

Check the activation and functionality of the various adjustment motors for the temperature doors in the front A/C unit, refer to Vehicle Diagnostic Tester in the "Guided Fault Finding " function.
Check the measured values of the various temperature sensors, refer to Vehicle Diagnostic Tester in the "Guided Fault Finding " Function.
Perform fault finding in the case of an increase in temperature after the evaporator, refer to FAULT FINDING IN THE CASE OF A TEMPERATURE INCREASE DOWNSTREAM FROM THE EVAPORATOR (IN THE FRONT A/C UNIT). .
Check the foam seal on the heat core for the heater of the front A/C unit, refer to HEATER CORE, REMOVING AND INSTALLING .
In vehicles with an Auxiliary Heater Heating Element -Z35-, check the separation between the left and right side in the front A/C unit via the installation shaft for the Auxiliary Heater Heating Element -Z35-, refer to AUXILIARY HEATER HEATING ELEMENT -Z35- WITH AUXILIARY AIR HEATER CONTROL MODULE -J604-, REMOVING AND INSTALLING, CHECKING .
Check the coolant circuit bleeding, refer to the appropriate service information .