Heater Core Case: Service and Repair
Heater Core
Special tools, testers and auxiliary items required
• Hose Clamps up to 25 mm Diameter (3094)
• Engine Bung Set (VAS 6122)
• Hose Clamp Pliers (VAS 6362)
Removal
There is a risk of scalding from hot steam and coolant.
• The coolant system is under pressure when the engine is warm.
• To reduce the pressure, cover the coolant reservoir cap with several cloths and then open it carefully.
- Open the coolant reservoir cap - arrow -.
- Note the general information => [ General Control Motor Information ] General Control Motor Information.
- Move the front seat as far back as possible.
- Use the button - 11 - to set the air flow direction to windshield.
• The air must come out of the defroster vent for the windshield.
• The figure shows the Comfort version of the control head.
- Switch off the ignition.
- Remove the plenum chamber cover and tower brace.
- Cover the area beneath the connections for the coolant hoses in the plenum chamber, for example, with absorbent paper.
- Label the arrangement of the coolant hoses.
• So that no coolant enters the plenum chamber when removing the coolant hoses, hold a container under the particular coolant hose.
- Clamp off the coolant hoses - 1, 4 - with hose clamps (3094) and remove from the heater core by releasing the hose clips - 2, 3 -.
- Attach a short hose - A, C - to both connections.
• Insert the compressed air gun - D - into the end of a hose.
- Hold the container - B - under the second hose and use the compressed air gun to carefully blow the coolant out of the heater core.
- Remove the driver side instrument panel cover.
- Remove the driver footwell vent. Refer to => [ Air Guide to Left Footwell Vent - Driver Side ] Air Guide to Left Footwell Vent - Driver Side.
- Remove the glove compartment.
- Remove the footwell vent on the front passenger side. Refer to => [ Right Footwell Vent Air Guide - Front Passenger Side ] Right Footwell Vent Air Guide - Front Passenger Side.
- Remove the air intake housing. Refer to => [ Air Intake Housing ] Air Intake Housing.
- Cover the floor covering in the area under the heater core with fluid-impermeable foil and absorbent paper.
• At the start of production, screw clamps made of metal are installed at the connections to the heater core. In the future, plastic clamps can also be installed. The use of these clamps has not yet been finalized.
Metal screw clamps
- Remove screws - A -.
- Remove the clamps - B -.
Plastic clamps
- Open and remove the clamps - A -, for example, with a screwdriver - C -
Continued for all
- Completely remove both braces - A - on the right on the air distributor housing.
- If present, unscrew the screw - F - and remove the bracket for the heater core - E -.
- Hold a container under the coolant pipes - 1, 4 -.
- Pull the coolant pipes out of the heater core - 3 - and carefully tilt to the side.
- Seal open lines and connections with a clean plug from the (VAS 6122).
- Press the heater core in the - direction of the arrow - out of the air distributor housing - 2 -.
• Depending on the version, it may not be possible to remove the heater core on the front passenger side. In this case, the heater core must be removed to the driver footwell side.
Remove the heater core at the driver footwell
- Remove the steering column.
- Remove the pedal assembly.
- Remove the bracket for the control motors on the left: Basic version, refer to => [ Bracket For Control Motors (V107)/(V108)/(V110) ] Bracket For Control Motors (V107)/(V108)/(V110), Comfort version, refer to => [ Bracket for the Control Motors (V110)/(V299) ] Bracket For the Control Motors (V110)/(V299).
- Hold a container under the coolant pipes.
- Pull the coolant pipes - 1, 3 - out of the heater core and carefully tilt to the side.
- Seal open lines and connections with a clean plug from the (VAS 6122).
- Pull the heater core in the - direction of the arrow - out of the air distributor housing - 2 -.
Installation
Installation is done is reverse order, observe the following:
• Replace the O-ring seals.
- Check the heater duct - C - for contamination with the heater core removed.
- Remove any dirt or residue from leaking coolant.
- Check the foam seals - B - attached to the heater core - A - for damage and replace if necessary.
• A foam seal that is not bonded correctly may curl up when inserted.
• Cold air may flow past the heater core if the foam seal is damaged or not properly fitted.
- Carefully push the heater core all the way into the A/C unit.
• When inserting the heater core, ensure that the connections and the coolant pipes are not damaged.
- Install the heater core bracket - E - on the air distributor housing and tighten with the screw - F -. Refer to => [ Comfort Version - Add On Parts of the A/C Unit Overview ] Comfort Version - Add On Parts of the A/C Unit Overview.
- Check the connection - 3 - of the heater core and the coolant pipes - 2 - for damage or contamination.
- Clean and smooth the sealing surfaces for the O-ring seal.
- Lightly moisten the new O-ring seal - 4 - with coolant (or lubricate lightly with silicone grease) and place on the coolant pipe - 1 -.
- Push the coolant pipes into the heater core to the stop.
Leaks in the heater core.
• Crushed O-ring seals or tilted or incompletely installed coolant pipes result in leaks.
Metal screw clamps
- Install new screw clamps - B - on the coolant pipe/heater core connection.
- Tighten the bolt - A - to 2 Nm.
- Check the screw clamps for proper seating on the connections of the heater core and the coolant pipes. They may not be in contact with the air distributor housing or other components.
Plastic clamps
Risk of scalding.
• Plastic clamps may only be used once since the clamping force of a used clamp is no longer sufficient and the coolant pipe will be pressed out of the heater core by the coolant pressure.
- Place the new plastic clamps - F - on the coolant pipe/heater core connection and press together.
- Check the clamps for proper seating and proper latching on the connections of the heater core and coolant pipes.
Continued for all
- Bleed the coolant circuit. Refer to => [ Bleeding the Coolant Circuit ] Bleeding the Coolant Circuit.
Check the connections at the heater core for leaks
- Carefully increase the pressure in the coolant circuit by using, for example, the hand pump of the Cooling system tester (V.A.G 1274/).
- Check the coolant circuit for leaks. Pay particular attention to the connection between the coolant pipes - D, E - and the heater core - A -.
• When bleeding coolant circuit, take special care to ensure complete bleeding of heater cores. 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 the vents at the same setting in regulated mode. Refer to => [ Heat Output and Temperature Door Activation, Checking ] Heat Output and Temperature Door Activation, Checking.
• Depending on vehicle equipment and on engine, heat insulation has been applied to coolant hoses, these must not be damaged and must be re-applied after installing.
- Install the bracket for the control motors on the left: Basic version, refer to => [ Bracket For Control Motors (V107)/(V108)/(V110) ] Bracket For Control Motors (V107)/(V108)/(V110), Comfort version, refer to => [ Bracket for the Control Motors (V110)/(V299) ] Bracket For the Control Motors (V110)/(V299).
- Install the pedal assembly.
- Install the steering column.
- Install the air intake housing. Refer to => [ Air Intake Housing ] Air Intake Housing.
- Install the footwell vent on the front passenger side. Refer to => [ Right Footwell Vent Air Guide - Front Passenger Side ] Right Footwell Vent Air Guide - Front Passenger Side.
- Install the glove compartment.
- Install the driver footwell vent. Refer to => [ Air Guide to Left Footwell Vent - Driver Side ] Air Guide to Left Footwell Vent - Driver Side.
- Install the tower brace.
After completion of the repair work, perform the following work on the control head using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function:
- Read out the event memory and erase any displayed entries.
- Perform the basic setting.
- Perform the output diagnostic test mode.
- Adjust the air flow direction at the different vents via various settings on the Climatronic control module (J255) , and check whether the quantity of air at the vents actually changes according to the setting.