A/C Unit
A/C Unit
Special Tools and Equipment
• Hose clamps up to diameter 25 mm (3094)
• Commercial compressed-air gun (with rubber end piece)
• Cooling system tester (V.A.G 1274) (and corresponding adapter)
A/C Unit, Preparing for Removal
• When the ignition is on, the valves of the pump/valve unit (Left Heat Regulation Valve (N175) and Right Heat Regulation Valve (N176)) are continually activated depending on the temperature set at the Climatronic Control Module (J255) A/C control head. For this reason, the valve may be warm or hot even when the engine is cold.
• If applicable, obtain radio anti-theft code before disconnecting battery.
• On vehicles with electrically adjustable seats, move seats to rearmost position before disconnecting battery.
- Drain the refrigerant circuit.
- Move power seats to rearmost position.
- Switch off ignition.
- Protect driver and passenger seat using seat cover.
- Detach ground connection from battery.
- Remove center console and instrument panel.
- Loosen the latches - B - and remove the air duct - A -.
- Remove instrument panel central tube (crossmember)
• In model year 2008, there is a rolling change in the threading at the screw points of the air distributor housing to the central tube of the instrument panel (the cast metal inserts have been eliminated, the screws go directly into the plastic), ensure the proper screw version during installation.
- Release pressure in cooling circuit by opening cap on coolant expansion tank.
- Clamp off coolant hose - A - (return from the heat exchanger to the engine) e.g. using hose clamps up to 25 mm dia. (3094).
- Mark the assignment of coolant hoses - A - (supply to left heat exchanger) and - B - (supply to right heat exchanger).
- Disconnect connector - D - to the Left Heat Regulation Valve (N175) and Right Heat Regulation Valve (N176).
- Disconnect connector - E - to the Coolant Pump (V50).
- Clamp off coolant hose - C - (from the engine to the Coolant Pump (V50)) e.g. using hose clamps up to 25 mm dia. (3094).
- Remove coolant hoses - A - and - B - from the pump/valve unit connections.
- Remove the sealing bolt from the bleeder valve - B -.
- Connect the section of hose - D - (extension) to the coolant hose - A -.
- Close the coolant hose - B - with a sealing plug - E -.
- Place a container - C - beneath the extension hose - D -.
- Using a compressed air gun (with rubber end piece) - F -, carefully blow coolant out of the driver side "heat exchanger" (into container - C -) via the open connection for the bleeder valve - G -.
- Remove the sealing plug - E - from the coolant hose - B - and insert in the coolant hose - A -.
- Connect the section of hose - D - (extension) to the coolant hose - B -.
- Using a compressed air gun (with rubber end piece) - F -, carefully blow coolant out of the front passenger side "heat exchanger" (into container - C -) via the open connection for the bleeder valve - G -.
- Remove the air intake unit => [ Air Intake Unit ] Air Intake Unit.
- Remove the refrigerant line from the connection to the A/C unit => [ Refrigerant Lines at A/C Unit ] Refrigerant Lines at A/C Unit.
- Remove coolant hoses that have already been marked (risk of transposition) from coolant pipes - A -, - B - and - C -.
- Remove grommets - E - and - F - from the coolant pipes.
- Remove grommet - H - from the connecting flange of the refrigerant lines - D -.
- Remove the grommet - G - of the air duct to the A/C unit.
Removing
- Perform the work to prepare the A/C unit for removal.
• On removal, note down bolt lengths and assignment for installation.
• All cable ties and other wiring harness fasteners released or cut open on removing air conditioner unit are to be reattached in same position on installation.
- Remove air ducts to vents in the center console => [ Air Routing and Distribution in Passenger Compartment ] Air Distribution in A/C and Air Intake Units, Block Diagram.
- Remove bolts - C -.
- Remove the air duct to the right footwell vent - B - (front passenger side).
- Remove bolts - C -.
- Remove the air duct to the right footwell vent - B - (front passenger side).
• In model year 2005, the footwell vent - B - air duct mount was changed (gradual introduction). The upper bolt - C - no longer has to be removed, the air duct clips in place via retaining tabs - A -.
- Check both condensation water drains of the A/C unit - A - => [ Condensation Drain Hose ] Condensation Drain Hose.
- Remove the cable duct - A - from the A/C unit (it is secured via the latches - B -).
- Remove the screws - B - (left and right at the center tunnel) and flip back the bracket - A -.
- Remove the A/C unit.
Installing
Installation is carried out in the reverse order, when doing this note the following:
• When inserting the A/C unit, be careful of the cables to the control motors and the seals. They must not be pinched or damaged.
• Check all seals and replace if necessary.
• Connect the coolant hoses to the heat exchanger at the correct side.
• Secure all hose connections with standard hose clamps or clips as used in series production, or approved replacement parts.
- Install the A/C unit.
- Install instrument panel central tube (crossmember)
• In model year 2008, there is a rolling change in the threading at the screw points of the air distributor housing to the central tube of the instrument panel (the cast metal inserts have been eliminated, the screws go directly into the plastic), ensure the proper screw version during installation.
- Install the holder between the A/C unit and the central pipe of the instrument panel.
- Flip the bracket- B - to the center tunnel and install the screws - B - (left and right at the center tunnel).
• Using the flexible bracket - A - installed at the A/C unit and the splines - B -, fluctuations in tolerance are balanced out and the A/C unit is centered with respect to the center tunnel.
- Reinstall all removed components in reverse order of removal except the lower instrument panel cover (driver's side), the glove compartment, and the plenum chamber cover.
• Connect the 2-pin harness connector to the Coolant Pump (V50) of the pump/valve unit only after bleeding the coolant circuit.
• The Coolant Pump (V50) (in the pump/valve unit) may only be operated after bleeding the coolant circuit.
• Dry running of pump in pump valve unit leads to destruction.
- Fill and bleed cooling circuit.
• When bleeding coolant circuit, take special care to ensure complete bleeding of heat exchangers. If air bubbles remain in heat exchangers, there may be complaints made by customers about insufficient heating performance in winter, or different air temperature from vents at same setting in regulated mode.
- After bleeding the cooling system, check it to ensure it is sealed tight. In particular, note the connections between the coolant pipes and the heat exchanger
- Check the position of the grommets in the coolant pipe feed through and at the refrigerant pipe connecting flange from the plenum chamber to the passenger area for proper seating.
- After installation, check the grommet between engine compartment and plenum chamber at the coolant hose - C - for proper seating.
- Check the pump/valve unit, it may not make contact with other components (noises).
- After bleeding the coolant circuit, connect the connectors - D - to the Left Heat Regulation Valve (N175) and Right Heat Regulation Valve (N176), and - E - to the coolant pump Coolant Pump (V50).
- Evacuate refrigerant circuit and refill it.
- After filling the refrigerant circuit, check the refrigerant line connection points in the plenum chamber and evaporator for leaks, e.g. using an electronic leak detector.
- Clean coolant residue from the plenum chamber.
- Install the remaining removed components again in reverse order.
- Check the DTC memory for the Climatronic Control Module (J255) A/C control head and erase any faults displayed if necessary.
- Perform a basic setting and output diagnostic test mode on the A/C system.
- Operate the A/C system after filling the refrigerant circuit => [ A/C System, Operating after Filling Refrigerant Circuit ] A/C System, Operating after Filling Refrigerant Circuit