Removal and Replacement
A/C Unit
Special tools, testers and auxiliary items required
• Hose Clamps, Up To 40 mm (3094) and Hose Clamps Up To 25 mm diameter (3093)
• Compressed air gun, commercially available
• Cooling System Tester (V.A.G 1274) (and corresponding adapter)
• Remove the heater in the same way as the A/C unit. Naturally, the items that affect components that are only present on the A/C system are omitted.
Removal
- Protect driver and front passenger seats using seat covers.
- Switch off ignition.
- Discharge the refrigerant circuit.
- Disconnect the battery.
• Obtain radio code if necessary before disconnecting battery.
• On vehicles with seats that can be adjusted electrically, move them all the way back before disconnecting the battery.
• On removal, note down bolt lengths and assignment for installation later.
• All cable ties opened or cut during removal of A/C (heater) must be reinstalled at the same locations during installation.
• Depending on vehicle equipment and on engine, heat insulation has been applied to coolant hoses and refrigerant lines, these must not be damaged and must be re-applied after installing.
- Release pressure in cooling circuit by opening the cap on coolant expansion tank.
- Remove components that hinder access to mounting points - A - on heat shield - B - and to coolant hoses to heater core in engine compartment. Refer to => [ Refrigerant Lines, Disconnecting and Connecting From Expansion Valve ] Refrigerant Lines, Disconnecting and Connecting From Expansion Valve.
- Loosen heat shield - B - from plenum chamber bulkhead (lay it aside or remove it completely).
- Mark arrangement of coolant hoses - A - and - B -.
• The heater core is designed for a specific coolant flow direction. Therefore, coolant hoses must be connected on the correct sides.
• Bleed the coolant circuit.
- Slide back thermal protective covers - D - and - E - far enough that (VAS 3093) - F - can be installed on the coolant hoses - A - and - B -.
- Clamp off coolant hoses - A - and - B -.
- Clamp off the ventilation hose - C - (to coolant expansion tank), with a (3094) - G -.
- Cover the area beneath connections for coolant hoses - A - and - B -, for example, with a paper towel.
- Remove coolant hoses - A - and - B - from connections to A/C unit heater core.
- Connect one section of hose - A - on to upper connection.
- Hold a container - B - under the lower connection - C -.
- Using a compressed air gun - D -, carefully blow coolant out of heater core (into container - B -).
- Disconnect refrigerant lines from expansion valve, refer to=> [ Refrigerant Lines, Disconnecting and Connecting From Expansion Valve ] Refrigerant Lines, Disconnecting and Connecting From Expansion Valve and secure (for example, with cable tie) so they do not interfere during installation.
• Seal open pipe connections.
• To seal off all open connections on expansion valve or evaporator, sealing caps from a replacement expansion valve or a replacement evaporator can be used (preventing dirt and moisture from entering the system).
- Remove glove compartment, driver's side storage compartment, front part of center console and instrument panel.
• To prevent the instrument panel shell from damage, instrument panel should be placed on a clean work bench which is covered with clean cardboard.
- Remove both left and right footwell vents.
- Remove the fresh air blower (V2). Refer to=> [ Fresh Air Blower Control Module (J126) and Fresh Air Blower (V2) ] Description and Operation.
- Remove instrument panel crossmember (central tube).
- Remove data bus on board diagnostic interface (J533) (secured to bracket - A - in area of steering column).
- Remove bolts - B - and release bracket - A - from heater (bracket remains on wiring harness secured to vehicle).
- Remove ESP Sensor Unit (G419) - A -.
- Loosen vehicle wiring harness fasteners - B - (for example, cable ties - C -) on left of A/C unit.
- Remove both bolts - A - on bracket for wiring harness - B -.
- Disconnect the connector - C -.
- Remove condensation drain from A/C unit. Refer to=> [ Condensation Water Drain Hose, Checking ] Testing and Inspection.
- Loosen remaining vehicle wiring harness fasteners (for example with cable ties) at top of A/C unit.
- Disconnect all electrical connections between vehicle wiring harness and the electrical components of A/C (on heater) at harness connectors.
• The wiring harness air conditioner/heater is removed together with the A/C unit (with the heater).
- Carefully pull right side of A/C (heater) unit slightly toward rear (far enough that bolt - B - on the right bracket - A - can be loosened).
• Only pull carefully on the A/C (heater) so that bracket - A - does not break.
• To loosen bolt - B -, reach between A/C unit (heater) and floor mat on right wheel housing (to make this possible, Fresh Air Blower (V2) has been removed earlier).
- Remove bolts - B - and release bracket - A - from heater (bracket remains on wiring harness secured to vehicle).
- Loosen securing ties of vehicle wiring harness on A/C (heater) on the right side.
- Disengage both flanges for coolant pipes to heater core - A - and for expansion valve (to evaporator) - B - from pass-through of grommet - C -.
• When removing A/C unit (heater), make sure the two coolant pipes of the heater core do not get caught and bent or damaged on plenum chamber or noise insulation mat.
• Observe wiring harness, individual electrical wiring connections may get damaged when pulling on harness.
- Remove A/C unit (heater) - A - towards passenger side.
Installation
Installation is carried out in the reverse order while noting the following:
- Two technicians are needed to install the A/C unit (heater).
• Before installing, check all gaskets and seals on A/C (heater) for damage and replace if necessary.
• Check securing of coolant pipes to heater core.
- Insert the molded seal - A - (working outward from the passenger compartment) into rear wall of the plenum chamber - B -, make sure that reinforcement - C - (wire bracket) is positioned correctly in the molded seal - A -.
• On vehicles without A/C system (heater only), insert molded seal - A - (working from passenger compartment) into rear wall of the plenum chamber - B -; make sure that molded seal - A - is positioned properly in rear panel.
- Ask a colleague for assistance when installing the A/C unit (heater).
- Have the second mechanic (working from engine compartment) guide both flanges for coolant pipes to heater core - A - and for expansion valve (to evaporator) - B - through pass-through of grommet - C - when inserting heating & A/C unit.
• When installing A/C/heater, make sure the two coolant pipes of the heater core do not get caught and bent or damaged on plenum chamber or noise insulation mat.
• Observe wiring harness, individual electrical wiring connections may get damaged when pulling on harness.
- Connect condensation water drain to connection on A/C unit and check condensation water drain for correct seating. Refer to=> [ Condensation Water Drain Hose, Checking ] Testing and Inspection.
- Reinstall removed components in reverse order of removal except driver's side storage compartment.
• When installing the instrument panel, make sure that the defrost intermediate piece its properly on A/C unit (heater) and the defrost vent does not pinch the intermediate piece. Refer to=> [ Air Routing and Distribution in Passenger Compartment ] Air Routing and Distribution in Passenger Compartment.
• After installing instrument panel, check output direction and distribution of air flow from defroster vent to windshield.
- Connect coolant hoses properly to heater core. Observe markings:
A Supply hose from cylinder head
B Return to the coolant pump
- Connect refrigerant lines to expansion valve. Refer to=> [ Refrigerant Lines, Disconnecting and Connecting From Expansion Valve ] Refrigerant Lines, Disconnecting and Connecting From Expansion Valve.
- Check installation position of coolant hoses to heater cores (they must not contact components which grow hot) and position and state of heat protection insulation applied to coolant hoses if necessary (not installed on all engine types).
- Bleed cooling circuit.
- Check coolant circuit for leaks, pay particular attention to the connection between coolant hoses and heater core. Refer to=> [ Heater Core ] Service and Repair.
- Make sure the grommet - C - fits correctly inside the rear panel of the plenum chamber.
- Seal flange for coolant pipes to heater core - A - and for expansion valve (to evaporator) - B - at pass-through of grommet - C - with silicon adhesive sealant if necessary (to prevent water from penetrating).
- Evacuate and re-charge refrigerant circuit.
- Reinstall driver side storage compartment and remaining removed components.
- Check Climatronic control module (J255) DTC memory and erase any possible displayed malfunctions using Vehicle diagnosis, testing and information system (VAS5051B) under "Guided Fault Finding".
- Perform a basic setting and output diagnostic test on the A/C (heater) and check the DTC memory one more time. Refer to Vehicle diagnosis, testing and information system (VAS5051B) under "Guided Fault Finding".
- Operate the A/C system after filling the refrigerant circuit. Refer to=> [ A/C System, Operating After Filling Refrigerant Circuit ] A/C System, Operating After Filling Refrigerant Circuit.
• Note the information regarding operating the A/C system after filling.
- If necessary, check A/C (heater) system function, for example, via "Output diagnostic test mode" function (allocation test of electrical component function) using Vehicle diagnosis, testing and information system (VAS5051B) under "Guided Fault Finding".