Heater Core With Front A/C Unit Installed
Heater Core With Front A/C Unit Installed
Special tools, testers and auxiliary items required
• Hose clamps up to 25 mm (3094) or hose clamps up to 40 mm (3093)
• Commercial compressed-air gun with rubber end piece
• Cooling system tester (V.A.G 1274) (and corresponding adapter)
Preparation For Removal
- Switch on the ignition.
- Set the air flow direction to DEF (toward the windshield) on the Climatronic control module (J255).
- Move the driver and passenger seats as far back as possible.
- Switch off the ignition.
- Remove the storage compartment under the instrument panel on the driver side.
- Remove the left footwell vent (driver side), refer to => [ Left Footwell Vents ] Left Footwell Vents.
- Remove the accelerator pedal module.
- Remove the glove compartment.
- Remove the right (front passenger) footwell vent, refer to => [ Right Footwell Vent ] Right Footwell Vent.
- Remove the air intake housing of the front A/C unit, refer to => [ Air Intake Housing Of Front A/C Unit ] Air Intake Housing Of Front A/C Unit.
• 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 the plenum chamber cover, refer to => [ Fresh Air Intake ] Service and Repair.
- Detach wiring harness - A - and put aside.
- Remove suspension strut dome - B -.
- Detach or remove engine control module - C - and remove the corresponding bracket.
- Remove fresh air intake - D - (only in vehicles with a rear A/C unit), refer to => [ Fresh Air Intake ] Service and Repair.
Removal
- 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/are 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.
- Clamp coolant hoses - C - and - B - with hose clamps - J -.
- If present, clamp coolant hose - D - with a hose clamp - J - (in vehicles with a rear A/C unit).
- Cover the area beneath connections for coolant hoses - A - and - B - for example with absorbent paper.
- Place a small container under the connections for coolant hoses - A - and - B - (to the heater core).
• To prevent coolant from entering the plenum chamber when removing coolant hoses - A - and - B -.
- Remove coolant hoses - A - and - B - from connections to A/C unit heater core.
- Insert one section each of hose - A - and - B - on to both connections to heater core.
- Place a container - B - under the other end of the hose - C -.
- Using a compressed air gun - D -, carefully blow coolant out of the heater core (against the normal flow direction of the coolant) via shaft - A - into container - B -.
- Cover the floor covering and the center tunnel under heater core - A - with a fluid-impermeable foil and absorbent paper.
- Label connector - F - (risk of confusion) and remove from the left footwell door motor (V108) (if this control motor was not removed).
- Secure wiring harness - G - to the A/C unit so that it does not get in the way when removing heater core - A -.
- Remove clamps - B - and - C - from the connections at heater core - A -.
• At the start of production, screw clamps are installed at the connections at heater core - A -. This figure shows a version with clamps - B - and - C - made of plastic. The implementation of these clamps is not yet finalized.
• At the start of production, metal screw clamps not plastic screw clamps - A - are available at coolant pipes - B - to the heater core.
Remove the screw clamps (metal clamps)
- Remove screw - A - at clamps - B - for coolant pipes - C - and - D -.
- Remove clamps - B -.
Remove the clamps (plastic)
- Open and remove plastic clamps - A -, for example with a screwdriver - C -
All
- Completely remove both braces - A - (on the right on the A/C unit).
• If the heater core was already replaced once, a bracket - E - and screw - F - are installed instead of braces - A -.
- Place a container under the connection for coolant pipe - D - at heater core - A -.
- Detach both coolant pipes - D - and - E - from the connections of heater core - A - and carefully tilt to the side.
- Remove heater core - A - in the direction of the arrow - arrow - from the A/C unit in the front passenger footwell.
• Depending on the version, it is possible in vehicles installed during the production period that heater core - A - cannot be removed in the direction of the arrow - arrow -. In this case, the heater core must be removed in the direction of the driver footwell.
Further procedure if the heater core cannot be removed from the A/C unit in the front passenger footwell:
- Remove the steering column and pedal assembly.
• 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 the bracket for the Left center vent motor (V110) and Left side vent motor (V299) => [ Bracket For Control Motors (V110) and (V299) ] Bracket For Control Motors (V110) and (V299).
• For this bracket to be able to be removed, the Defroster door motor (V107) , Left center vent motor, and Left side vent motor must be removed.
- Remove the bracket for the Left footwell door motor (V108) and Left footwell temperature door motor (V411) => [ Bracket For Control Motors (V108) and (V411) ] Bracket For Control Motors (V108) and (V411).
• To remove the heater core, the bracket for the Left footwell door motor and Left footwell temperature door motor does not necessarily have to be removed. However, to achieve better accessibility and better freedom of movement, it is helpful to remove this bracket.
• For this bracket to be able to be removed, the Left footwell door motor and Left footwell temperature door motor must be removed.
- Remove heater core - A - against the direction of the arrow - arrow - into the driver footwell.
Installation
Installation is carried out in the reverse order while noting the following:
- Check seals - B - on heater core - A -. Only install a heater core with seals that are not damaged and are glued on securely.
• If not bonded correctly, seal - B - can curl up during insertion.
• If a seal - B - is damaged or is not properly installed, cold air can flow past the heater core which can result in complaints due to cold air from the A/C unit or noises.
- Check both connections - C - of heater core - A - for damage or dirt.
- Check the A/C unit for contamination via installation shaft - C - (the shaft for the heater core) and if present installation shaft - D - (for the auxiliary heater heating element (Z35) , only in vehicles with a diesel engine).
- Remove any dirt or coolant which has leaked out from the A/C unit (for example, after removing a leaking heater core).
- Check upper and lower installation shaft - C - on both sides of the A/C unit with respect to the edges or protruding material.
- Remove any material left on the tool separation points during production of the A/C unit and round any edges.
• During production of the A/C unit, edges can be created at the tool separation points or material that protrudes beyond the A/C unit can remain. At these points, the connections for the coolant pipes at the heater core can be damaged during installation.
- Carefully push heater core - B - all the way into the A/C unit.
• When inserting heater core - A -, ensure that both connections - B - and both coolant pipes - D - and - E - are not damaged.
- Install bracket - E - and screw - F -.
• Bracket - E - and screw - F - are available as a replacement part. Refer to Electronic Parts Catalog.
• In vehicles in which heater core - A - was removed in the driver footwell, insert heater core - A - in the direction of the arrow - arrow - into the A/C unit to the stop
- Lightly moisten both connections - B - of heater core - A - with coolant or grease them with silicone grease.
• The silicone grease part number is G 000 405 A2. Refer to Electronic Parts Catalog.
- Check the connection area of both coolant pipes - D - and - E - to the heater core for damage or contamination.
- Lightly moisten new seals - C - (contained in the heater core delivery) with coolant (or grease lightly with silicone grease).
- Install new seals - C - on both coolant pipes - D - and - E -.
- Insert both coolant pipes - D - and - E - with each seal - C - into the connections of heater core - B - and push them in to the stop.
• Do not bend the coolant pipes - D - and - E - when pushing them into the connections on the heater core.
- Make sure seals - C - between coolant pipes - D - and - E - in connections - B - of heater core - A - fit securely.
Seals that are incorrectly installed or jammed - C - will leak.
• The seals - C - must be installed completely into both the coolant pipe connections - D - and - E - and the flange connections - B -.
Install the screw clamps (metal clamps)
- Remove screw - B - from new clamps - A -.
- Remove screw - A - at clamps - B - for coolant pipes - C - and - D -.
- Install new clamps - B - on coolant pipe - C - and - D - and turn clamps - B - so that screw - A - can be installed.
- Press coolant pipes - C - and - D - consecutively into the heater core and install a clamp - B - as shown on the connection point to the heater core.
• The clamp - B - engages when it is pressed in.
- Screw one screw - A - into each clamp and secure clamp - B - by tightening screw - A - (bolt tightening specification is 2 Nm).
- Check clamps - B - for proper seating on the connections of the heater core and the coolant pipes.
- Check the installation position of clamps - B - and screws - A -. They must not be in contact with the A/C unit or other components.
Install the clamps (plastic)
• Currently not provided (introduction not yet finalized). In the meantime, metal screw clamps are available as a replacement part. Refer to Electronic Parts Catalog.
- Install new plastic clamps - F - (if included in the heater core delivery) on coolant pipes - D - and - E -.
Only use plastic clamps - F - once.
• Always install new clamps - F -. Refer to Electronic Parts Catalog..
- Attach plastic clamps - F - as shown at the connection points between the heater core and coolant pipes - D - and - E - and press together.
• Clamp - F - engages when pressed together.
- Check the seating and latching of clamps - F - on coolant pipes - D - and - E -.
All
- Make sure the grommet - H - fits correctly in the back of the plenum chamber.
- Properly connect the coolant hoses to the heater core, pay attention to the marking.
A Supply from the coolant recirculation pump (V50)
B Return to the engine
- Connect coolant hose - A - to the heater core coolant pipe (pay attention to the marking) and secure it with a clamp.
- Install the coolant hose to heater core - B - on the coolant pipe so that air can still escape when ventilating the coolant circuit (do not push all the way on).
- Remove hose clamp - J - from coolant hose - C -.
- Fill the coolant overflow reservoir with coolant.
- Screw the hand pump of the cooling system tester (V.A.G 1274/) onto the filler neck of the coolant expansion tank.
- Carefully force the coolant out of the coolant overflow reservoir into the heater core using, for example, the hand pump from the Cooling System Tester (V.A.G 1274/).
- As soon as the coolant escapes from the connection point between coolant hose - B - and the coolant pipe of the heater core, push coolant hose - B - completely onto the coolant pipe.
- Secure coolant hose - B - with a clamp.
- Remove hose clamp - J - from coolant hose - B - (and - D -).
- Open bleeder screw - G - and further ventilate the coolant circuit via bleeder screw - G -.
- If necessary, add more coolant overflow reservoir with coolant.
• By this procedure, the cooling system is not completely bled. If, for some other reason, there still should be some air in the cooling system, install all the components and bleed the system once again.
Check the connections on the heater core for leaks as follows:
- Carefully increase the pressure in the cooling system by using, for example, the hand pump from the Cooling System Tester (V.A.G 1274/).
- Check the coolant circuit for leaks. Pay particular attention to the connection between coolant hoses - D - and - E - and 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 vents at 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.
- Reinstall all removed parts in the reverse order.
- Perform the basic setting and the output diagnostic test mode (for function check) of the A/C system using the Vehicle Diagnostic Tester 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 setting, the control motors are assigned and adapted corresponding to the switching sequence of the wiring. If this sequence does not conform with the specification, the control motors will adapt incorrectly and the door control will be wrong => [ A/C Control Motor Block Diagram ] A/C Control Motor Block Diagram.
- Check the event memory of the Climatronic control module, and erase any displayed malfunctions using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.
- Direct the air flow direction via various settings on the Climatronic control module to the different vents and check whether the air coming out at the vents actually changes according to the setting.