Heater Core, Heating & A/C Unit Installed
Heater Core, Heating & A/C Unit Installed
Special tools, testers and auxiliary items required
• Hose Clamps Up To Diameter 25 mm (3094)
• Compressed air gun, commercially available
• Cooling System Charger (VAS 6096) (hand pump and corresponding adapter)
Preparatory Work
- Protect driver and passenger seat using seat cover.
- Switch ignition on.
- On vehicles with electric seats, move these completely toward rear.
- Switch ignition off.
- Dissipate pressure in coolant circuit by opening cap at coolant expansion tank.
- Remove windshield wiper completely.
- Remove right and left sections of plenum chamber front wall - A - and - B -.
• 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 -.
• 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).
• Depending on version of vehicle, 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.
- Mark arrangement of coolant hoses - A - and - B - to heating & A/C unit.
- Cover section of plenum chamber under connections of coolant hoses to heater core of heating & A/C unit with absorbent paper.
- 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 lower left instrument panel trim..
- Remove accelerator pedal module.
- Remove Brake Light Switch (F) with its retainer (do not loosen brake light switch from retainer).
- Disengage bracket for control modules and relay carrier which is mounted in left area next to heating & A/C unit from instrument panel transverse member and remove bracket.
• Relays and control modules themselves are not removed, rather are to be stored in footwell in such a way that they do not hinder other work or become soiled or damaged.
- Remove air channel for air duct in driver's footwell.
- Remove left cover of heater core, refer to => [ Left Heater Core Covers - Heating & A/C Unit Installed ] Left Heater Core Covers - Heating & A/C Unit Installed.
- Remove lower right instrument panel trim.
- Remove glove compartment.
- Remove air channel for air duct in front passenger's footwell.
- Remove right cover of heater core, refer to => [ Right Heater Core Covers - Heating & A/C Unit Installed ] Right Heater Core Covers - Heating & A/C Unit Installed.
- Detach floor carpet on right and left sides of center tunnel and fold it carefully back far enough that it is not damaged during other work and that it does not interfere.
- Cover floor mat in footwell and on center tunnel in area below heater core connections with leak-proof foil and absorbent paper.
Removing
- Pull off retaining clips - A - from coolant lines - B - and - C -.
- Pull coolant lines - B - and - C - out of heater core and turn them so that they no longer interfere when continuing removal.
- Remove bolts - D -.
- Turn retaining pin - A - out of locking mechanism - B -
- Pull retaining pin - A - out of lower air duct - C - and heating & A/C unit - arrow -.
- Release catches - E - of lower air guide - C -
- Fold lower air duct - C - with heater core downward as far as possible (in direction of - arrow - - F -) and then pull both components together toward rear as far as possible.
- Remove lower air duct - C - together with heater core in direction of driver's footwell.
Installing
• The assistance of a second technician is required for installation of heater core.
- Clean front heating & A/C unit - D - and lower air duct - B - (for example, of residual coolant).
- Check foam seals - C - at heater core - A -, they must be glued all around without gaps and must not be damaged.
- Insert heater core - A - on proper side into lower air duct - B -.
- Install heater core - A - together with lower air duct - B - into heating & A/C unit - D -.
• While inserting, make sure that groove/spring connection between heating & A/C unit - D - and lower air guide - B - is joined correctly.
- Insert retaining pin - A - for connecting lower air duct - C - to heating & A/C unit.
- Turn retaining pin - A - into locking mechanism - B -
- Then check fit of retaining pin - A - in heating & A/C unit and in air duct (also via front passenger's side).
- Install bolts - D -.
- Moisten new O-ring seals - D - (included in heater core delivery casing, refer to the Electronic Parts Catalog) lightly with coolant.
- Insert new seals - D - on to coolant pipe connections - F -.
- Push both coolant pipes - B - and - C - into heater core connections - E -.
- Insert retaining clips - A - on proper side on to coolant lines - B - and - C - and heater core connections.
• Only use retaining clips of standard used in series production, refer to the Electronic Parts Catalog.
- Check retaining clips - A - on coolant pipes and heater core connections again for secure fit.
- Re-install both covers on left and right sides of heater core and the remaining removed components in passenger compartment in reverse order except for lower left instrument panel lining.
- 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 ] 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 Cooling System Tester (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 ] Coolant System, Bleeding.
• Bleed cooling circuit, refer to => [ Coolant System, Bleeding ] Coolant System, Bleeding.
- 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.
- Install the remaining removed components in engine compartment again in reverse order.
- Check coolant circuit for leaks, pay particular attention between coolant hoses and heater core.
• Before bleeding, check the seal of the cooling circuit. For example, using hand pump from Cooling System Tester (V.A.G 1274/).
- Install lower left instrument panel lining and other removed components.
- Bleed cooling circuit, refer to => [ Coolant System, Bleeding ] Coolant System, Bleeding.
• 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 ] Heating Performance Of A/C System, Checking.
- Check DTC memory of Climatronic Control Module (and of Rear A/C Display Control Head (E265) ) and erase any DTCs displayed using the Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function.
- If necessary, perform a basic setting and output diagnostic test mode on the A/C system using the Vehicle Diagnosis, Testing and Information System VAS5051 in the "Guided Fault Finding" function.
- Check function of A/C system if necessary.