Heating Performance Of A/C System, Checking
Check the functionality of the Coolant Recirculation Pump -V50-, the Water Pump -V36-, the Coolant Shut-Off Valve -N82- and the Auxiliary Heater Heating Element -Z35-.
Starting with MY 2009, certain vehicles with a 6 cylinder TDI engine without an auxiliary heater, have an Auxiliary Air Heater Heating Element -Z35- installed depending on the emissions standard (running change depending on the engine). Refer to the AUXILIARY HEATER HEATING ELEMENT Z35 , Audi Sales Program.
Diesel vehicles without a fuel driven auxiliary heater (or the optional equipment parking heater) have an auxiliary heater heating element near the heater core. The air leaving the heater core in the front of the A/C unit is also heated by the auxiliary heater heating element.
Auxiliary heater heating element) removing and installing refer to AUXILIARY HEATER HEATING ELEMENT Z35 , checking refer to AUXILIARY HEATER HEATING ELEMENT Z35, CHECKING .
If coolant circuit is not completely bled after filling, air may accumulate in heater cores of heating & A/C units or heating & A/C units, 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. Bleed coolant circuit COOLANT SYSTEM, BLEEDING if necessary.
Depending on engine, coolant circulation for the A/C system is ensured by various pumps or these pumps support the engine coolant pump with engine running. Vehicles with an 8 cylinder engine or a 6 cylinder TDI engine have a coolant pump -V50-. 6 cylinder gasoline vehicles have a water pump -V36-. A 6 cylinder gasoline vehicle with a parking heater as an optional equipment has both a water pump -V36- and a coolant pump -V50-. Refer to INCORPORATION OF FRONT HVAC SYSTEM INTO COOLING CIRCUIT .
If customer complains of poor heating performance at specific engine speeds, check incorporation of A/C system in the coolant circuit. If both coolant hoses (supply and return) from engine via Coolant Pump -V50- (Coolant Pump -V36-) to heater core is interchanged, the engine coolant pump works against Coolant Pump -V50- (Coolant Pump -V36-) and coolant no longer flows into heater core(s) at certain engine speeds. Refer to INCORPORATION OF FRONT HVAC SYSTEM INTO COOLING CIRCUIT , and [For engine(s) BAR] Description and Operation .
Diesel vehicles without a fuel driven auxiliary heater / without the optional equipment parking heater) have an auxiliary heater heating element near the heater core. Refer to AUXILIARY HEATER HEATING ELEMENT Z35 . The air leaving the heater core is also heated by the auxiliary heater heating element. Check the activation and function of the auxiliary heater heating element, refer to AUXILIARY HEATER HEATING ELEMENT Z35, CHECKING and Vehicle Diagnosis, Testing and Information System VAS 5051 in"Guided Fault Finding" .
From MY 2014, a Coolant Shut-Off Valve -N82- is installed on certain engines without the optional "parking heater". The coolant shut-off valve -N82- is activated by the Climatronic Control Module -J255- front A/C control head (via the Engine Coolant Shut-Off Valve Relay -J541-), when no heat is desired in the passenger compartment. Refer to COOLANT SHUT-OFF VALVE -N82- and Wiring diagrams, Troubleshooting & Component locations. In the event that the heating output on these vehicles is lacking, additionally check the actuation and functionality of the coolant shut-off valve -N82-. Refer to the Vehicle Diagnostic Tester in "Guided Fault Finding" .
On vehicles with Comfort version A/C system, the specified temperatures themselves can be measured or read out via the "Read measuring value block" function using Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" .
If the vehicle has a Basis A/C system, the specified temperatures must be measured manually. The vehicle does not have a temperature sensor for this, refer to Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" .