Heater Core Case: Service and Repair
Heat Exchanger
=> [ Preparation for Heat Exchanger Removal ]
=> [ Right Heat Exchanger ]
=> [ Left Heat Exchanger ]
=> [ Rear Footwell Heater ]
Preparation for Heat Exchanger Removal
- Switch off ignition.
- Release pressure in cooling circuit by opening cap on coolant expansion tank.
- Remove left and right plenum chamber covers.
- Remove the engine control module and the E-box cover.
- Disconnect 2-pin connector from Coolant Pump (V50) of pump valve unit. Refer to => [ Pump Valve Unit, Checking ] Pump Valve Unit, Checking.
- Mark the arrangement of coolant hoses - A - supply to pump valve unit and - B - return to engine.
- Clamp off two coolant hoses from engine to pump valve unit using Hose Clamps (V.A.G 3094).
- Remove coolant hoses - A - and - B - from connections.
- Connect one hose piece - A - and - B - to each of two connections.
- Place container - C - beneath hose - B -.
- Clamp off return from passenger's side heater core - D -, using a hose clamp.
- Using compressed-air gun, carefully blow coolant out of driver's side heater core and pump valve unit into container.
- Remove hose clamp from hose - D -.
- Clamp off return from driver's side heater core - B -, using a hose clamp.
- Using compressed-air gun, carefully blow coolant out of passenger's side heater core and pump valve unit (into container).
- Remove hose clamp from hose - B -.
- Loosen bolt - A - for coolant pipe holder in plenum chamber approximately 2 turns.
- Remove coolant line bracket - B -.
- Lightly coat contact surface of both coolant pipes - D - and - E - at boot - C - with silicone lubricant so that pipes can be moved without changing position of boot.
Right Heat Exchanger
Special tools, testers and auxiliary items required
• Hose Clamps (3093 bzw. 3094)
• Compressed air gun, commercially available
• Cooling System Tester (V.A.G 1274)
• Remove the left heat exchanger first on right hand drive vehicles.
• The right heat exchanger must be removed to remove the left one on left hand drive vehicles.
Removing
- Perform preparatory work for removing heater core. Refer to=> [ Preparation for Heat Exchanger Removal ]
- Remove glove compartment.
- Remove footwell vent.
- Cover carpet in area under heat exchanger with waterproof foil and water absorbing paper.
- Lightly coat contact surface of both coolant pipes - D - and - E - at boot - C - with silicone lubricant from inside as well so that pipes can be moved without changing position of boot, this illustration shows pipes viewed from plenum chamber.
- Remove clamps - A - and - B -.
- Take both coolant pipes out of heat exchanger.
- Push both coolant pipes in direction of "plenum chamber".
• As grommet has been moistened slightly with silicone lubricant in area of coolant pipe penetration, pipes can be moved without grommet being pushed out of air conditioner unit.
- Remove bolts - C -.
- Detach holder.
- Pull heater core - D - out of air conditioner.
Installing
- Before installing heater core, check openings - A - of condensate drain for soiling and clean if necessary.
• Condensate drain must not be blocked by dirt or other deposits.
• Drain openings in illustration are depicted with heater cores installed.
Cleaning condensate drain:
- Heat exchanger removed: Insert illuminated angled mirror into opening for heat exchanger and check both drain openings. Clean condensate drains if necessary using a piece of wire, for example.
- Heat exchanger with condensate hose detached, clean condensate drains from outside using a piece of wire, for example.
Perform further installation in reverse order, paying attention to the following:
- Before installing heater core, check attached foam seal
• An incorrectly glued seal can roll up into air conditioner when sliding in heater core.
• Cold air may flow past heat exchanger if seal is damaged or not properly fitted.
- Secure all connections with standard clamps or with retainers approved for these connections.
• Clamps - A - and - B - can only be mounted with difficulty in installed position.
• To replace the heat exchanger when the A/C unit is installed, use clamping brackets - A - and - C -.
- Check both coolant pipes - B - and heater core connections - C - for soiling or damage.
• Sealing rings must always be replaced.
- Lightly coat sealing ring - A - with coolant and place on coolant pipe - B -.
- Place clamping bracket - A - (with studs) according to illustration onto connection at heater core - B -.
- Place clamping bracket - C - (with holes) onto coolant pipe - D - according to illustration.
- Insert coolant line - D - (with sealing ring) into connection of heater core - B -.
- Secure coolant pipe with two clamping brackets - C - and - D - in heater core.
- Tighten both hex nuts - A - and - B - alternately and uniformly (tightening torque 3 Nm).
• Clamping brackets - C - and - D - must be installed as illustrated observe outer contour.
• When tightening hexagon nuts, take care not to tilt retainers.
• After securing coolant pipes, check position of retainers. They must not make contact with other components.
- Install second coolant pipe in the same way.
- Before installing glove box, check cooling system for leaks.
- Before installing glove box and plenum chamber cover, check position of grommet in coolant pipe penetration to plenum chamber.
- Connect the 2-pin connector to the pump valve unit Coolant Pump (V50) after bleeding the coolant circuit. Refer to => [ Pump Valve Unit, Checking ] Pump Valve Unit, Checking
• Coolant Pump (V50) of pump valve unit must only be operated after coolant circuit has been vented, dry running of pump in pump valve unit leads to destruction.
• When bleeding coolant circuit, take special care to ensure complete bleeding of heat exchangers. If air bubbles remain in heater cores, 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. Refer to => [ Ventilation System Heat Output and Pump Valve Unit Function ] Ventilation System Heat Output and Pump Valve Unit Function.
Left Heat Exchanger
Removing
- Remove right heater core. Refer to => [ Right Heat Exchanger ].
• Because of the pedal cluster on left hand drive vehicles, the left heat exchanger can only be removed toward the passenger footwell with the right heat exchanger removed.
• The left heat exchanger must be removed on right hand drive vehicles to remove the right heat exchanger.
- Remove driver storage compartment.
- Completely remove gas pedal module.
- Remove left footwell vent.
- Cover carpet in area under heat exchanger with waterproof foil and water absorbing paper.
- Remove clamps - A - and - B -.
- Remove coolant pipes - C - and - D - from heater core - E -.
- Slide heater core - E - in direction of passenger side perpendicular through air conditioner.
Installing
- Before installing heater core, check attached foam seal
• An incorrectly glued seal can roll up into air conditioner when sliding in heater core.
• Cold air may flow past heat exchanger if seal is damaged or not properly fitted.
Installation is carried out in the reverse order, when doing this note the following:
• Sealing rings must always be replaced.
• To prevent heater core from sliding back into air conditioner, it is appropriate to insert heater core for passenger side into air conditioner and to secure bracket with bolt - C -.
- Push heat exchanger from front passenger side sideways through air conditioner unit.
- Install O-rings, coolant pipes and brackets the same way they were installed for the left heater core => [ Right Heat Exchanger ].
- Before installing glove compartment, storage compartment on passenger's side and plenum chamber cover, check position of boots - C - and - D - in coolant pipe penetration to plenum chamber.
- Check coolant system for proper seal before installing glove compartment and storage compartment on driver's side.
- Further installation work steps are to be performed in same manner as described for heater core on passenger's side. Refer to=> [ Right Heat Exchanger ].
Rear Footwell Heater
• The Climatronic Control Module (J255) front A/C control head activates the Left Rear Footwell Heater (Z42) and Right Rear Footwell Heater (Z43) via a data line. The activation is shown in the measured value block vehicle diagnosis, testing and information system VAS 5051 in the "Guided Fault Finding" function.
• Heater element consists of control module, temperature sensor and, at present, 4 transistors with heat sinks which generate heat and supply it to the passing air flow.
• Heater element is installed only on vehicles with Rear A/C Control Head (Climatronic) (E265) in vent - C - optional equipment.
Removing
- Switch off ignition.
- Remove left or right seat.
- Remove cover - A -.
- Lift floor covering - B -.
- Disconnect harness connector to heater element.
- Remove vent - C - with heater element.
Installing
Install in reverse order of removal.