Front HVAC Unit
Special tools and workshop equipment required
- Hose Clamps Up To Diameter 25 mm3094
- Compressed air gun, commercially available
- Cooling System TesterV.A.G 1274 (and corresponding adapter)
Preparatory work to remove front heating & A/C unit
-- Protect driver and passenger seat using seat cover.
-- Switch ignition on.
-- On vehicles with electric seats, move these completely toward rear.
-- Switch off ignition.
-- Discharge the refrigerant circuit. Refer to REFRIGERANT CIRCUIT, SERVICING .
Before disconnecting Battery, obtain anti-theft radio security code if necessary.
On vehicles with electrically adjustable seats, move the seats back as far as possible before disconnecting the Battery.
-- Disconnect negative terminal clamp from Battery. Refer to BATTERY .
-- Dissipate pressure in coolant circuit by opening cap at coolant expansion tank. Refer to [For engine(s) BAR] General Information .
-- Remove fresh air intake shaft for heating & A/C unit. Refer to FRESH AIR INTAKE HOUSING .
-- Remove windshield wiper completely. Refer to WINDSHIELD WIPER BLADES, REMOVING AND INSTALLING .
-- Remove right and left sections of plenum chamber front wall -A-. Refer to PLENUM CHAMBER BULKHEAD, REMOVING AND INSTALLING .
Right and left sections of plenum chamber front wall -A- and -B- are secured to vehicle by bolts -C- and -D-. Seals -E- and -F- are installed between both sections of plenum chamber front wall and vehicle body.
-- Remove center section of plenum chamber front wall -A-. Refer to PLENUM CHAMBER BULKHEAD, REMOVING AND INSTALLING .
Center section of plenum chamber front wall -A- is secured to vehicle by bolts -B- and nuts -C-. A seal -D- is installed between plenum chamber front wall and vehicle body.
Nuts -C- are loosened only, not removed (slots are present on plenum chamber front wall).
Depending on engine, various engine components must be removed so that nuts -C- can be loosened (for example, air intake hoses and/or upper engine cover). Refer to (diesel) [For engine(s) CNRB] Removal and Installation and (gasoline) [For engine(s) BHK] Removal and Installation .
Depending on version of vehicle and of engine, various lines (electrical wires, fuel and vacuum lines, etc.) are secured to plenum chamber front wall -A-, disengage them from plenum chamber front wall -A- if necessary.
-- Remove front expansion valve, refer to FRONT EXPANSION VALVE .
After removing expansion valve, connections to evaporator must be sealed with sealing caps -A- and -B- and thus prevent the penetration of dirt and moisture as well as damage when removing and installing, refer to FRONT EXPANSION VALVE .
-- Mark arrangement of coolant hoses -A- and -B- to heating & A/C unit.
-- Clamp off coolant hoses to heater core of heating & A/C unit (for example, using 3094) and remove them.
-- Release grommet -C- from plenum chamber rear wall and slide grommet -C- into passenger compartment.
-- Insert one section each of hose -A- and -B- on to both connections to heater core.
-- Hold a container -C- under hose of lower connection -B-.
-- Using a compressed air gun -D-, carefully blow coolant out of heater core (into container -C-) via hose -A-.
-- Remove dash panel complete with dash panel cross member. Refer to INSTRUMENT PANEL, REMOVING AND INSTALLING .
To prevent the instrument panel shell from damage, instrument panel should be placed on a clean work bench which is covered with clean cardboard.
Removing front heating & A/C unit
On removal, note down bolt lengths and assignment for installation later.
All cable ties and other wiring harness fasteners released or cut open on removing air conditioner unit are to be attached again in same position on installation.
-- Preparatory work to remove front heating & A/C unit has been performed.
-- Remove air ducts to footwell vents -A- and -B-.
Versions of footwell vents -A- and -B- vary on vehicles with and without rear heating & A/C unit, this illustration shows the version on vehicles with rear heating & A/C unit, refer to AIR DUCTS IN AND TO FRONT AND REAR HEATING & A/C UNIT .
-- Remove condensation water drain hose from heating & A/C unit, refer to FRONT CONDENSATION WATER DRAIN HOSE .
-- Mark the installation position of washers of hex nuts -C- on plenum chamber rear wall for example, using a waterproof marker.
-- Remove hex nuts with washer -C-
A rubber base -D- is glued on to washer of hex nuts -C- as a seal.
-- Check fit of sealing caps -A- and -B- on connections to evaporator, they must fit securely so that the connections are not damaged when removing the heating & A/C unit.
-- Disconnect harness connector -A-.
-- Disengage bracket for wiring harness -B- from heating & A/C unit -D-.
-- Release the remaining anchors of wiring harness on heating & A/C unit -D- (for example, cable ties -C-).
Starting with MY 2009, certain vehicles with a 6 cylinder TDI engine have an Auxiliary Heater Heating Element -Z35- installed depending on the emissions standard (running change depending on the engine). Refer to Audi Sales Program. Loosen the line connections on vehicles with an auxiliary heater heating element. Refer to AUXILIARY HEATER HEATING ELEMENT Z35
-- Remove A/C unit -A- from vehicle in direction of front passenger side.
Installing front heating & A/C unit
Installation is carried out in the reverse order while noting the following:
-- The assistance of a second technician is necessary to install the A/C unit.
-- Check bonded rubber elements -A- for correct fit in heating & A/C unit (glue them into mounts of heating & A/C unit -F- if necessary).
-- Check fit of sealing caps -B- and -C- on connections to evaporator, they must fit securely so that the connections are not damaged when installing the heating & A/C unit.
-- Check foam seal -D- for proper fit and damage.
-- Check boot -E- for proper fit on flange of coolant pipes and for damage.
Before installing, also check all other gaskets and seals on the heating & A/C unit for damage and replace if necessary.
-- Insert heating & A/C unit and secure them to plenum chamber rear wall with both hex nuts with washer -C-.
Make sure that hex nuts -C- are in the correct position on plenum chamber rear wall when tightening (corresponding to markings applied)
Only install hex nuts with washer -C- on which the rubber base -D- has been glued on as a seal and are not damaged.
-- Re-install all bolts corresponding to the arrangement during removal.
-- Re-install all cable ties that were opened or cut during air conditioner removal at the same locations during installation.
-- Connect condensation water drain hose to heating & A/C unit, refer to FRONT CONDENSATION WATER DRAIN HOSE .
-- Install the instrument panel transverse member and secure heating & A/C unit to instrument panel transverse member at the designated mounting points. Refer to INSTRUMENT PANEL, REMOVING AND INSTALLING .
-- Insert grommet -C- into plenum chamber rear wall and then check fit of grommet -C- on flange of coolant pipes (in passenger compartment).
-- Connect coolant hose -A- to coolant pipe to heater core (coolant hose -B- is not connected for the time being).
Connect coolant hoses on proper side, coolant hose -A- supply from engine (via pipe group under left fender) and coolant hose -B- return to engine (via pipe group under left fender), refer to INCORPORATION OF FRONT HVAC SYSTEM INTO COOLING CIRCUIT .
-- Fill coolant into coolant expansion tank up to top marking.
-- Open 3094 on coolant hose -A- far enough that coolant can flow slowly into heater core (to pre-bleed heater core).
If coolant does not flow into heater core on its own, pressure can be built up in coolant expansion tank using hand pump of V.A.G 1274 and thereby accelerate the flow.
By pre-bleeding the cooling circuit, bleeding of the cooling system after installation is greatly simplified on first starting in operation, refer to COOLANT SYSTEM, BLEEDING .
Bleed cooling circuit, refer to COOLANT SYSTEM, BLEEDING and [For engine(s) BAR] General Information .
-- Wait until coolant exits from coolant hose connection -B- on coolant pipe to heater core.
-- Connect coolant hose -B- at coolant pipe to heater core.
-- Except for the cover under left side instrument panel, re-install the remaining removed components in reverse order.
-- Evacuate and re-charge refrigerant circuit. Refer to OPERATING AFTER FILLING REFRIGERANT CIRCUIT .
Note the information regarding operating the A/C system after filling in OPERATING AFTER FILLING REFRIGERANT CIRCUIT .
-- Check coolant circuit for leaks, pay particular attention between coolant hoses and heater core. Refer to [For engine(s) BAR] Diagnosis and Testing .
After filling, check the coolant circuit for leaks as follows: open cap on coolant expansion tank (observe safety precautions when opening cap. Refer to [For engine(s) BAR] Diagnosis and Testing ) and then increase pressure in cooling circuit for example, using hand pump from V.A.G 1274/. Refer to [For engine(s) BAR] Diagnosis and Testing .
-- Bleed cooling circuit. Refer to COOLANT SYSTEM, BLEEDING and [For engine(s) BAR] General Information .
When bleeding coolant circuit, take special care to ensure complete bleeding of heater core. If there are still air bubbles in the heater core, it may cause the customer to complain of insufficient heating performance in winter or different air temperature from vents at same setting in regulated mode, refer to HEATING PERFORMANCE OF A/C SYSTEM, CHECKING .
-- Install the lower left instrument panel lining.
-- Check DTC memory of Climatronic Control Module and of Rear A/C Display Control Head -E265- and erase DTCs displayed if necessary using the Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" .
-- Perform a basic setting and output diagnostic test mode on the A/C system using the Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" .
-- Operate the A/C system after filling the refrigerant circuit, refer to OPERATING AFTER FILLING REFRIGERANT CIRCUIT .
-- Check function of A/C system if necessary using the Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" .