Front Heating and A/C Unit
Front Heating and A/C Unit
Special tools, testers and auxiliary items required
• Hose clamps up to 25 mm diameter (3094) and hose clamps up to 40 mm diameter (3093)
• Commercial compressed-air gun with rubber end piece
• Cooling system tester (V.A.G 1274) (and corresponding adapter)
• 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 re-attached in same position on installation.
Removing
- Remove the driver and front passenger seat.
- Switch off ignition.
- Drain the refrigerant circuit.
- Disconnect the ground cable from the battery.
• The ground connection of the battery is disconnected so that a short circuit cannot occur when removing the A/C unit.
- Remove the plenum chamber front wall.
- Release pressure in cooling circuit by opening cap on coolant expansion tank.
- Label the arrangement of the coolant hoses at the connections to the heater core - A - (supply from the coolant recirculation pump (V50) ) and - B - (return to the engine).
• This figure shows the arrangement of the coolant hoses in a vehicle with a rear A/C unit and a parking heater. In vehicles without a rear A/C unit, coolant hoses - D - and - F - are not present, for example => [ Incorporation of A/C System in Coolant Circuit ] Incorporation of A/C System in Coolant Circuit.
• The heater core(s) is installed in the A/C units so that a specific flow direction of the coolant is necessary for clean ventilation of the heater core. Therefore, the coolant hoses must be connected on the correct side, refer to => [ Incorporation of A/C System in Coolant Circuit ] Incorporation of A/C System in Coolant Circuit.
• Bleed the coolant circuit, refer to => [ Coolant Circuit, Bleeding ] Coolant Circuit, Bleeding.
- Remove both coolant hoses from the coolant pipes to the heater core in the front A/C unit, refer to => [ Heater Core With Front A/C Unit Installed ] Heater Core With Front A/C Unit Installed.
- Blow out the coolant in the heater core, refer to => [ Heater Core With Front A/C Unit Installed ] Heater Core With Front A/C Unit Installed.
- Loosen the grommet - H - from the plenum chamber rear wall and remove it from the heater core coolant pipes.
- Remove the expansion valve, refer to=> [ Front Expansion Valve ] Front Expansion Valve.
• Seal open pipe connections.
• To seal off all open connections on expansion valve, sealing caps from a replacement expansion valve can be used (preventing dirt and moisture from entering the system).
- Remove the expansion valve mounting plate - A - from the refrigerant lines - B - and - C - (so that it does not get lost while removing).
- Coat the inner side of the grommet - D - with grease and remove the supporting ring - E -.
- Loosen the grommet - D - from the plenum chamber rear wall toward the passenger compartment (it is removed and installed with the A/C unit).
- Remove the base support of center console - A - and insulation mat - B -.
• A/C system malfunctions in the case of interchanged control motors and/or connectors, refer to => [ A/C Control Motor Block Diagram ] A/C Control Motor Block Diagram.
• The control motors and connectors are identical. If they are installed or connected incorrectly, the corresponding doors cannot be properly adapted and/or activated.
• Clearly label control motors and connectors prior to removal to prevent incorrect installation.
- Remove bolts - A -.
- Push air duct - C - forward (to the front A/C unit), and then lift at the back and remove in the - direction of the arrow -.
• The removal of A/C unit - B - is subsequently described so that instrument panel cross member - A - remains in the vehicle. The A/C unit can also be removed together with the air intake housing and the instrument panel cross member while ensuring that no other components (for example wire connections, door trim, door sills, etc.) are damaged.
• To remove the A/C unit together with the instrument panel cross member, it is not necessary to first remove the air intake housing and the A/C unit may not be detached from the instrument panel cross member. All other steps are to be performed as described below. In addition, it must be ensured when removing this assembly that all wire connections between the A/C unit and the instrument panel cross member, including covered connections, have been disconnected.
- Remove the glove compartment and instrument panel - A - and.
• To prevent the instrument panel shell from damage, instrument panel - A - should be placed on a clean work bench covered with clean cardboard, for example.
• When removing instrument panel - A -, ensure that no wire connections are damaged (for example the wire to the sunlight photo sensor (G107) , which is routed through instrument panel - A - and the defroster vent).
- Remove air intake housing - G -, refer to => [ Air Intake Housing Of Front A/C Unit ] Air Intake Housing Of Front A/C Unit.
- Remove steering column - B - (or only detach from instrument panel cross member - H - and place so that will not be damaged).
- Remove the air duct with the defroster door for left and right instrument panel vent/side window - C - and - D -, refer to => [ Air Duct To Instrument Panel Vent and Left Side Window ] Air Duct To Instrument Panel Vent and Left Side Window and => [ Air Duct With Defroster Door For Instrument Panel Vent/Right Side Window ] Air Duct With Defroster Door For Instrument Panel Vent/Right Side Window.
- Remove the air ducts to left and right instrument panel vents - E - and - F -, refer to => [ Air Duct To Instrument Panel Vent and Left Side Window ] Air Duct To Instrument Panel Vent and Left Side Window and => [ Air Duct To Instrument Panel Vent and Right Side Window ] Air Duct To Instrument Panel Vent and Right Side Window.
• The air guide to left instrument panel vent - C - is attached to an expanding rivet - A - on instrument panel cross member - B -.
• Expanding rivet - A - of the left air duct can only be removed and installed with the instrument panel removed.
- Detach the air ducts to the air distributor housing/rear A/C unit - A -, center instrument panel vent - B -, and defrost vent - C - from the A/C unit (release catches - D - on the air ducts) and remove.
- Remove bolt - E - and remove tab - F - from the A/C unit or turn it so that it is not in the way during removal of the A/C unit.
• A/C unit - G - is secured to center tunnel - H - via bolt - E -, ribs - G - and tab - F -.
- Remove bolts - A -.
- Detach the wire connection to A/C unit - D - from the other wires on the center tunnel and attach to A/C unit - D -.
• The wiring harness air conditioner is removed together with the A/C unit.
- Disconnect both condensation water drains - A - and - B - from the A/C unit connections.
- Disconnect all additional connections between A/C unit - B -, instrument panel cross member - A - and the vehicle.
- Disconnect the fuse panel on the left and right side of instrument panel cross member - A - from the instrument panel cross member.
• Since instrument panel cross member - A - is only detached from the vehicle (not completely removed), the remaining relay/fuse carriers and connector stations must not be removed from instrument panel cross member - A -.
- Cover the floor covering in the area of the center tunnel with a mat - E -.
- Detach instrument panel cross member - A - from the vehicle.
• Instrument panel cross member - A - must not be completely removed in order to remove the A/C unit. It is sufficient to disconnect it from the vehicle and the A/C unit, to swivel it to the right and to the rear and then to place it on the center tunnel.
- Carefully detach instrument panel cross member - A - from the vehicle and carefully tilt it back - arrow - (so that components are not damaged by any not yet detached connections) so that A/C unit - B - can be removed to the right - arrow -.
When tilting back instrument panel cross member - A -, components and electrical connections can be damaged.
• Work carefully.
• When tilting back instrument panel cross member - A -, always ensure that no electrical connections are being pulled or otherwise damaged.
- Remove the coolant pipes to heater core - C - and grommet - D - from the openings in the rear wall of the plenum chamber and carefully detach A/C unit - B - (so that no components are damaged by any still attached connections) slightly from the vehicle and remove it in the direction of the front passenger footwell - arrow -.
Installing
Installation is carried out in the reverse order while noting the following:
• Prior to installation, check all seals and grommets on A/C unit - B - for damage and replace damaged parts.
- Install A/C unit - B - and the components removed with the A/C unit (wiring harness "A/C unit", grommet on the refrigerant lines to evaporator - D -, etc.) in the vehicle.
- Install instrument panel cross member - A -.
- Use bolts - A - to attach the A/C unit to instrument panel cross member - B -.
- Coat the grommet - D - with grease and install it in the plenum chamber rear wall.
- Install the support ring - E - in the grommet - D -.
- Install the expansion valve mounting plate - A - to the refrigerant lines - B - and - C -.
- Install grommet - H - for the coolant pipes to the heater core in the plenum chamber rear wall.
- Check the position of the coolant and refrigerant lines in both grommets in the plenum chamber rear wall, and if necessary, align the A/C unit so that the lines are not tensioned in the grommets.
- Install the air intake housing, refer to => [ Air Intake Housing Of Front A/C Unit ] Air Intake Housing Of Front A/C Unit.
- Insert tab - F -, slide all the way to the bracket, then turn it downward (when doing this, mount - G - locks the A/C unit to the tab).
- Install bolts - E -.
- Install the air ducts to the air distributor housing/rear A/C unit - A -, to center instrument panel vent - B - and to defrost vent - C -.
• When installing air ducts - A -, - B - and - C -, ensure proper seating and leak-proof connection of the components. If the connection points are not leak-proof, noises can result from escaping air or the escaping warm or cold air can affect the regulation of the A/C system.
- Install the steering column.
- Install the expansion valve, refer to => [ Front Expansion Valve ] Front Expansion Valve.
- Connect both condensation water drain hoses to the A/C unit, refer to => [ Front Condensation Water Drain Hose, Checking ] Front Condensation Water Drain Hose, Checking.
- Install both coolant hoses on the coolant pipes to the heater core in the front A/C unit, bleed the coolant circuit as described with the engine off, and check for leaks. Refer to => [ Heater Core With Front A/C Unit Installed ] Heater Core With Front A/C Unit Installed and => [ Heater Core With Front A/C Unit Installed ] Heater Core With Front A/C Unit Installed.
- Secure the wiring harness once again on the provided places and install the different air guides in reverse order.
- Reinstall the instrument panel, center console, glove compartment, etc..
• When installing the instrument panel, make sure that the defrost intermediate piece its properly on A/C unit and the defrost vent does not pinch the intermediate piece, refer to => [ Air Routing and Air Distribution In Front Passenger Compartment ] Air Routing and Air Distribution In Front Passenger Compartment.
- Install the remaining removed parts in the opposite order.
- Reconnect the battery ground connection; when doing this, pay attention to the notes regarding reconnecting the battery.
- Evacuate and fill the refrigerant circuit.
- Perform the basic setting and the output diagnostic test mode of the A/C system using v in the "Guided Fault Finding" function.
• In this vehicle, the control motors are equipped with electronics. During the basic setting, a new control motor learns its position on the A/C unit and can then be activated by the Climatronic control module (J255) (currently all control motors are identical). Check using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
• During the basic adjustment, the control motors are assigned and adapted corresponding to the switching sequence of the wiring. If this sequence does not conform the specification, the control motors will adapt incorrectly and the door control will be wrong (A/C control motors block diagram)
- Check the event memory of the Climatronic control module (J255) , and erase any displayed malfunctions using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- 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.