Heating, Ventilation: Diagnosis Audi A3 8P facelift

SEAT HEATER ACTIVATION, TESTING

Special tools and workshop equipment required

1. Test Box 105 Pin V.A.G 1598/42-1 and Test Adapter V.A.G 1598/47
2. Vehicle Diagnostic, Testing and Information System VAS 5051 A with Multimeter Leads VAS 5051/7

Scheme 135

Scheme 136

1. The Heater Control Module -J65- provides a voltage via the Heated Driver Seat Adjuster -E94- and Heated Front Passenger Seat Adjuster -E95- (a potentiometer is operated via the respective knurled wheel -C-).
2. The voltage supplied by Heater Control Module -A- with seat heater switched on is dependent on the knurled wheel position and on the vehicle voltage supply, it is in the range of less than 0.5 volts in position 0 to approximately 10 volts in position 5 (measured to GND e.g. at connector -B- terminal 20) with engine running. The voltage is transferred via connector -B- (from terminal 11 to Driver Seat Heater Control Module -J726- and from terminal 15 to Front Passenger Seat Heater Control Module -J727-). Refer to appropriate SYSTEM WIRING DIAGRAM.

Note. Resistance of seat heater potentiometer is dependent on the knurled wheel position, it cannot be measured using workshop equipment. Check function of seat heater and service it. and appropriate SYSTEM WIRING DIAGRAM. Beginning with MY 2009 and as a running change, seat heating control modules are being installed that control the seat heating temperature at a lower characteristic curve. From MY 2010, this vehicle has a Start/Stop System for specific engines as optional equipment. On vehicles with the Start/Stop System, seat heating is switched off whenever the Stop function is active (by the Vehicle Electrical System Control Module -J519- to protect the battery). After the engine is started again by the Start function, seat heating is switched on again. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".

ENGINE CONTROL MODULE (ECM) ACTIVATION, TESTING

Special tools and workshop equipment required

1. Test Box 105 Pin V.A.G 1598/42-1 and Test Adapter V.A.G 1598/47
2. Vehicle Diagnostic, Testing and Information System VAS 5051 A with Multimeter Leads VAS 5051/7

Note. These functions are dependent on the version of the engine and of the ECM and are not present on all vehicles. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding" (for the respective ECM) and appropriate SYSTEM WIRING DIAGRAM. On vehicles with a manual climate control system, the A/C Control Module -J301- exchanges the information via the data bus system with each ECM. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".

1. The Heater Control Module -J65- has a potentiometer installed. This potentiometer is operated via rotary switch for temperature preselect -A- and therefore transmits position of temperature dial to ECM.

On vehicles with diagram-mapped cooling, activation of Map Controlled Engine Cooling Thermostat -F265- is influenced by the respective ECM on certain engines. If rotary switch for temperature preselect -A- is located at Warm stop or closely in front of it, coolant temperature is reduced (limited to approximately 95 °C) to prevent excessive air blower temperatures from heater air vents. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" function (for respective ECM).

In vehicles with gasoline direct fuel injection engine FSI, mixture formation is influenced by respective ECM on certain engines. If rotary switch for temperature preselect -A- in area of Warm stop or closely in front of it, improved coolant heating (and thus better heating performance) is attained by departing the stratified charge range for engine mixture formation and the engine runs normally. Check using Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function (for respective ECM).

In vehicles for which this function is designated, a voltage of approximately 5 volts is supplied the ECM at connector -B- between terminal 1 and 10 with ignition switched on. Check using Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function (for respective ECM) and appropriate SYSTEM WIRING DIAGRAM.

A voltage between approximately 0.5 V (cold) and approximately 4.5 V (warm) is sent via terminal 2 inside the connector -B- to the heater control module -A- depending on the position of the temperature preset rotary switch -A- Each ECM knows the position of the temperature preset rotary switch -A- by this voltage. The ECM evaluates this voltage and then controls the coolant temperature and the mixture formation. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" function.

AUXILIARY AIR HEATER HEATING ELEMENT - Z35- ACTIVATION, TESTING (WITHOUT A/C)

Special tools and workshop equipment required

1. Test Box 105 Pin V.A.G 1598/42-1 and Test Adapter V.A.G 1598/47
2. Vehicle Diagnostic, Testing and Information System VAS 5051 A with Multimeter Leads VAS 5051/7

Only installed on vehicles with Diesel engine

Note. An electric auxiliary air heater is currently installed in vehicles with diesel engine. In this system, the air is supplied with heat energy after it has left the heater core of the heater in the event a there is a request from the heater controls (Heater Control Module -J65-). The electric auxiliary air heater is controlled by the Auxiliary Air Heater Control Module -J604- or by the Engine Control Module (ECM) (on the 3-stage version by the Low Heat Output Relay -J359- and the High Heat Output Relay -J360-). Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function for respective ECM and appropriate SYSTEM WIRING DIAGRAM. The electric auxiliary air heater is available in different versions. On vehicles equipped with a diesel engine built through November 2006 (running change) the control of the Auxiliary Air Heater Heating Element -Z35- via the auxiliary air heater control module. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function. On vehicles with Diesel engine manufactured later than November 2006 (running change in production), a 3-stage Auxiliary Air Heater Heating Element is installed, which is actuated via a relay by the ECM. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function for respective ECM and appropriate SYSTEM WIRING DIAGRAM. At this time, an Auxiliary Air Heater Heating Element is also installed in vehicles with Diesel engine and parking heater as optional equipment. At a later point in time (not yet finalized), the auxiliary air heater heating element will be discontinued, then the parking heater undertakes the function of the auxiliary heater. Functional testing of the electric auxiliary air heater activation on a vehicle with a auxiliary air heater control module is described in Guided Fault Finding of the A/C system using Vehicle Diagnosis, Testing and Information System VAS5051. Measuring value block of auxiliary air heater control module indicates that auxiliary heater is switched on or why no activation is occurring despite a request. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding". Functional testing of the electric auxiliary air heater activation on a vehicle with a 3-stage auxiliary air heater heating element is described in Guided Fault Finding of the respective ECM using Vehicle Diagnosis, Testing and Information System VAS5051. At this time, no auxiliary heater is installed in vehicles with gasoline engine, also the parking heater is not activated as auxiliary heater. From MY 2010, this vehicle has a Start/Stop System for specific engines as optional equipment. On vehicles with the Start/Stop System the auxiliary air heater heating element is switched off when the Stop function is active (to protect the battery). After the engine started with the Start function, the auxiliary air heater heating element is switched on again. Refer to Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".

Check Activation Of Heater Controls (Heater Control Module -J65-)

1. The heater control module has a switch. This switch is operated (closed) via rotary switch for temperature preselect -A- in area from approximately 3 o'clock position up to "warm" stop.

If the switch for the auxiliary heater is closed, then the electronics in the heater control module will switch through terminal 7 ground to the auxiliary air heater control module -J604- / to the respective engine control module with the ignition turned on. Auxiliary air heater control module / ECM detects that additional heating performance is desired and switches on the electric auxiliary heater when the other switch-on requirements necessary for activation have also been met.

1. Switch-on conditions for electric auxiliary air heater (activation of Auxiliary Air Heater Heating Element) from the Auxiliary Air Heater Control Module. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" function.
2. Switch-on conditions for parking heater as auxiliary heater (in Auxiliary Heater Control Module) on vehicles with this optional parking heater.
3. Switch-on conditions for electric auxiliary air heater (activation of Auxiliary Air Heater Heating Element) from ECM. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" function for ECM.

Note. In order for each ECM to control the 3-stage Auxiliary Air Heater Heating Element via the Low Heat Output Relay and the High Heat Output Relay, the ECM must fulfill the same conditions, which are also required in the A/C Control Module -J301- on vehicles with a manual A/C system. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.

Switch-On Criteria For Electric Auxiliary Air Heater Activation

The ECM actuates Auxiliary Air Heater Heating Element via Low Heat Output Relay and High Heat Output Relay in the event the following requirements are met

1. There is a GND signal at ECM from Heater Control Module.
2. Engine is running for a minimum of 8 seconds and engine speed is greater than 500 RPM.
3. Engine temperature is lower than 75 °C.
4. The calculated outside air temperature is lower than 8 °C.
5. Vehicle voltage supply is greater than 12.2 volts and no request that forbids the switch-on is sent by Vehicle Electrical System Control Module -J519-.
6. No DTC is stored in ECM and generator load is less than 30 to 77% (depending on engine speed).

Note. On vehicles with a 3-stage auxiliary air heater heating element, the ECM actuates both relays for auxiliary heater in such a way that generator load does not exceed 95 %. Check using Vehicle Diagnosis, Testing and Information System VAS 5051 in the "Guided Fault Finding" (for ECM) and appropriate SYSTEM WIRING DIAGRAM. Thus the next stage is switched on only in the event generator load is less than 30 to 77%, depending on engine speed.

Switch-Off Criteria For Auxiliary Heater Activation

Note. On vehicles without A/C system, activation is switched off as soon as one of the switch-on requirements is no longer met in ECM or one of the switch-off criteria is detected.

1. When one of the switch-on requirements is no longer met.
2. The calculated outside air temperature is higher than 11 °C.
3. Generator load is greater than 95%.
4. There is no longer a GND signal at ECM from Heater Control Module.