A/C Unit Heat Exchanger
A/C Unit Heat Exchanger
Special tools, testers and auxiliary items required
• Hose clamps up to 25 mm diameter (3094)
• Standard compressed air gun with rubber nozzle
Heat Exchanger, Preparing for Removal
- Switch off ignition.
CAUTION!
There is a risk of scalding from hot steam and coolant.
• The refrigerant system is under pressure when the engine is warm.
• To reduce the pressure, cover the coolant reservoir cap with cloths and open it carefully.
- Open the coolant reservoir cap.
- Remove the center tunnel cover - 1 -.
- Remove the driveshaft.
CAUTION!
There is a risk of burns.
• The heat regulating valve unit may be warm or hot even when the engine is cold because it is continuously activated when the ignition is on depending on the temperature setting on the Climatronic control module.
- Clamp off the coolant supply hose - A - to the heat regulating valve unit - B - and the coolant hose - C - from the central heat exchanger return - D - with hose clamps (3094).
- Remove the coolant hoses - A and C -.
- Connect a hose to each heat regulating valve unit (to the extension) and to the heat exchanger central return.
- Place a reservoir - F - under the hose - E -.
- Place the compressed air gun - A - (with rubber nozzle) on the hose - B -.
- Carefully blow the coolant out of the heat exchangers via the return line by pressing the coolant hoses - C and D - together.
- Seal the central return line with a sealing plug.
- Remove the glove compartment.
- Remove the bolt - A - and the footwell vent air channel - B -.
- Remove the driver side instrument panel cover.
- Remove the bolt - B - and the footwell vent air channel - A -.
- Remove the front center console.
- Remove the left central tube bracket on the center tunnel.
• The coolant pipes may be secured to the heat exchanger in different ways:
• If they are secured with screw clamps - B -, remove the bolt - C - to open.
• If they are secured with clamping sleeves - A -, open the sleeve, for example with a screwdriver - C -.
Removal
- Cover the floor mat in the center tunnel area at the left and right under the heat exchanger with a waterproof cover and absorbent paper.
- Remove the bolt - H - on the coolant line connection - G -.
- Remove the coolant line connection from the coolant lines to the heat exchanger.
- Loosen the bolts - A, C and F - several turns so the coolant lines can move in the brackets - B, D and E -.
- Place a container under the coolant pipe connection.
- Remove the clamps - B and D -.
- Remove the coolant pipes - A and C - from the heat exchanger.
- Remove the bolt - D - and bracket - C - for the heat exchanger - B -.
- Place a container under the coolant pipe connection.
- Remove the clamp - E -.
- Remove the coolant pipe - A - from the heat exchanger.
- Remove the heat exchanger - B - to the right from the A/C unit - arrow -.
Installing
• There are different versions of the heater core and the associated coolant pipes. However, the version with an axial/radial seal - A - and - B - was not used on the Audi R8. A radial seal - D - and - E - is always installed.
Check the following before installing the heat exchanger:
• Check the heat exchanger foam seals - A - for damage and to see if they are bonded correctly (the foam seals must not come loose when installing the heat exchanger).
• Seal may curl up on insertion if not correctly bonded on.
• Cold air may flow past heat exchanger if seal is damaged or not properly fitted.
• Always replace the seals and clamps.
- Check the connections on the heat exchanger - B -, - C - and - D - for damage and contamination.
- Check the A/C unit heat through the heat exchanger installation shaft for contamination or coolant residue. Clean if necessary.
- Slide the heat exchanger - A - into the A/C unit from the right so the left and right sits flush with the A/C unit housing. Make sure the seal - B - does not roll up or become damaged.
- Position the bracket - C - for the heat exchanger - B - on the A/C unit.
- Tighten the bolt - D -.
• Note the different diameter of the seals and clamps for the coolant pipes - A and D -.
Proceed as follows if secured with a screw clamp:
- Remove the bolt - C - from the new clamp - B -.
- Position the new clamp - B - on the coolant pipe - E - so it can be secured as shown in the illustration.
- Lightly coat the seal - D - with coolant and place it on the coolant pipe - E -.
- Insert the coolant pipe - E - in the heat exchanger - A -.
- Press the coolant pipe into the heat exchanger and position the clamp - B - on the connecting point to the heat exchanger as shown in the illustration.
• The clamp - B - engages when it is pressed in.
- Insert the bolt - C - in the clamp and tighten it to secure the clamp.
- Repeat the procedure on the remaining heat exchanger coolant lines.
Proceed as follows if secured with a clamping sleeve:
- Position the new clamp - A - on the coolant pipe so it can be secured as shown in the illustration.
- Lightly coat the seal with coolant and insert it on the coolant pipe - B -.
- Insert the coolant pipe - B - in the heat exchanger.
- Press the coolant pipe into the heat exchanger and position the clamp - A - on the connecting point to the heat exchanger as shown in the illustration.
• The clamp - A - engages when it is pressed in.
• Disregard - item C -.
- Repeat the procedure on the remaining heat exchanger coolant lines.
- Replace the seals- B and -on the coolant lines - A -.
- Check the holes in the coolant line connection - D - for ridges or damage.
- Check if the bolts - A, C and F - are still loosened. The coolant line connection - G - can only slide on if they are.
- Slide the coolant line connection - G - onto the heat exchanger up to the coolant lines.
CAUTION!
• The coolant line connection must be absolutely parallel to the heat exchanger coolant lines.
• When sliding the coolant line connection on, make sure the seals on the coolant lines to the heat exchanger are not crushed.
- Carefully tighten the bolt - H - on the coolant line connection - G -.
• Tightening specification: 9 Nm.
- Tighten the bolts - A, C and F -.
- Connect the coolant hoses - A and C -.
- Remove the hose clamps (3094).
• The Coolant Pump (V50) can only be operated after bleeding the coolant circuit (running the coolant pump dry will destroy it).
- Disconnect the electrical connector - D - on the coolant pump - C -.
• Disregard the remaining items.
• Both heat regulating valves must be open to bleed the coolant circuit (they are open when they are not activated).
- Disconnect the electrical connector - D - on the heat regulating valve unit.
• Disregard the remaining items.
- Fill and bleed the coolant circuit.
- Connect the connectors to the coolant pump and the heat regulating valve unit.
• If the ignition is switched on with the connector disconnected, the Climatronic control module will detect and store malfunctions for the coolant pump and heat regulating valves.
- Adjust the heating and A/C system to maximum output on the Climatronic control module (temperature rotary knob to warm, fresh air blower knob to the highest level).
- Start engine.
- Let the engine run for 5 minutes at 2500 RPM and check if there are still noises coming from the coolant pump.
• If there are no more noises, stop the engine and check the coolant level.
• When bleeding coolant circuit, take special care to ensure complete bleeding of heat exchangers. If there are still air bubbles in the heat exchanger, it may results in insufficient heat output in the winter or different air temperatures coming out of the vents in control mode.
- While bleeding, check if the coolant line connection at the coolant lines to the heat exchanger has leaks. If necessary, remove the coolant line connection and replace the seals.
- Install the driveshaft.
- Install the center tunnel cover.
- Install the left and right footwell vents, refer to => [ Air Routing and Distribution in Passenger Compartment ] Air Routing and Distribution In Passenger Compartment.
- Install the front center console.
- Install the glove compartment.
- Install the driver side instrument panel cover.
After finishing the repairs, perform the following work on the Climatronic Control Module (J255) using Vehicle diagnosis, testing and information system VAS 5051/ in the "Guided Fault Finding" function:
- Check the DTC memory and erase any malfunctions shown.