Evaporator Core: Service and Repair
Evaporator
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)
• Heavy-duty gloves to protect against cuts
• Stable sharp knife with a tip (e.g. stable carpet knife)
Evaporator, Preparing for Removal
- Drain the refrigerant circuit.
• When the ignition is on, the valves of the pump/valve unit (Left Heat Regulation Valve (N175) and Right Heat Regulation Valve (N176)) are continually activated depending on the temperature set at the Climatronic Control Module (J255) A/C control head. For this reason, the valve may be warm or hot even when the engine is cold.
- Switch off ignition.
- Release pressure in cooling circuit by opening the cap on coolant expansion tank.
- Remove the plenum chamber cover.
CAUTION!
Even when the engine is cold, both pump/valve unit valves can be hot.
- Remove the windshield wiper arm, cowl panel trim, and complete windshield wiper
- If necessary, remove the dome brace (not present in all vehicles).
- Clamp off coolant hose - A - (return from the heat exchanger to the engine) e.g. using hose clamps up to 25 mm dia. (3094).
- Mark the assignment of coolant hoses - A - (supply to left heat exchanger) and - B - (supply to right heat exchanger).
- Disconnect connector - D - to the Left Heat Regulation Valve (N175) and Right Heat Regulation Valve (N176).
- Disconnect connector - E - to the Coolant Pump (V50).
- Clamp off coolant hose - C - (from the engine to the Coolant Pump (V50)) e.g. using hose clamps up to 25 mm dia. (3094).
- Remove coolant hoses - A - and - B - from the pump/valve unit connections.
- Remove the sealing bolt from the bleeder valve - B -.
- Connect the section of hose - D - (extension) to the coolant hose - A -.
- Close the coolant hose - B - with a sealing plug - E -.
- Place a container - C - beneath the extension hose - D -.
- Using a compressed air gun (with rubber end piece) - F -, carefully blow coolant out of the driver side "heat exchanger" (into container - C -) via the open connection for the bleeder valve - G -.
- Remove the sealing plug - E - from the coolant hose - B - and insert in the coolant hose - A -.
- Connect the section of hose - D - (extension) to the coolant hose - B -.
- Using a compressed air gun (with rubber end piece) - F -, carefully blow coolant out of the front passenger side "heat exchanger" (into container - C -) via the open connection for the bleeder valve - G -.
- Remove the glove compartment.
- Remove the driver side storage compartment beneath the instrument panel (not for vehicles with right-hand steering).
- Remove the right and left side panels of the center console.
- On the right side remove the holder - A - for the glove compartment.
- Remove bolts - C -.
- Remove the air duct to the right footwell vent - B - (front passenger's side).
- On the left side remove the holder - A - for the cover below the instrument panel.
- Remove bolts - C -.
- Remove the air duct to the right footwell vent - B - (front passenger's side).
• In model year 2005, the footwell vent - B - air duct mount was changed (gradual introduction). The upper bolt - C - no longer has to be removed, the air duct clips in place via retaining tabs - A -.
- Remove the pedal cluster.
- In the area to the right of the center tunnel, cover the floor mat under the connection for the coolant pipe - D - (or to the left for right-hand steering) under the heat exchanger, using a film impervious to fluids and absorbent paper.
- Remove the bracket - A - for the coolant pipe - D -.
- Remove the clamp - E -.
- Place a container under the connector for the coolant pipe - D - at the heat exchanger.
- Remove the coolant pipe - D - from the heat exchanger
- Remove the coolant hoses that have already been marked (risk of transposition) from the connectors - B - and - C -.
- Remove the grommet - A -.
- Depending on the vehicle equipment, remove the electric control modules and corresponding holders preventing the removal of the evaporator (e.g. the Front Information Display Control Head Control Module (J523))
Removing
• Perform preparatory work for removing the evaporator.
- Release the thermal insulation - A - from the refrigerant line connection flange at the evaporator - E - (to the left at the A/C unit).
- Remove the screws - B -.
- Release the connecting flange - A - (of the refrigerant lines) from the connection flange - D - (at the evaporator - E -).
- Remove the screw - A - on the bracket for the coolant pipe (to the right at the A/C unit, do not remove), and put the coolant pipe - D - off to the side.
- Put on the heavy-duty gloves (to protect your hands when separating the A/C unit housing wall).
- Separate the housing wall - B - and - C - (on the right side of the A/C unit) using a sharp knife (for example, a strong carpet knife with a point; the blade must be secure and the handle must be strong.) along the cut line - E - from the A/C unit.
• Make sure the flange - F - is not damaged (it seals the cover to the A/C unit).
- Remove the evaporator - E - to the right from the A/C unit.
• If the evaporator gets stuck in the A/C unit because of the rubber seal around it, remove the dust and pollen filter if necessary => [ Dust and Pollen Filter ] Dust and Pollen Filter to get a better hold on the evaporator.
Installing
Installation is carried out in the reverse order, when doing this note the following:
- Clean the evaporator installation shaft - A - in the A/C unit.
- Check both connections - C - and - D - in the evaporator connecting flange of the refrigerant lines - B - for dirt and damage, and clean if necessary.
• To replace the refrigerant lines - B - with the evaporator connecting flange, the air intake unit has to be removed, and the refrigerant lines to the A/C unit disconnected. In addition, the coolant lines to the heat exchanger on the left side have to be disconnected and removed.
- Before installing the evaporator, check the water drain hose openings - F - (at the left and right in the A/C unit) for dirt and clean them if necessary.
- Place the plastic frame - C - on the evaporator - A -.
- Place the surrounding rubber seal - B - on the evaporator - A -, ensure that the evaporator connecting flange - D - is seated properly.
- Replace O-ring seals - E - and - F - on connectors - D - on the evaporator - A -.
• Coat the O-ring seals lightly with refrigerant oil before installing.
• Make sure O-rings - E - and - F - are seated properly in groove in the connecting pipes to evaporator connecting flange - D -.
• There is refrigerant oil in the removed evaporator that must be returned to the refrigerant circuit.
- Lightly coat the rubber seal - B - on the top and bottom of the evaporator with lubricant (e.g. a soap solution).
- Carefully install evaporator - E - in slot - A - of the A/C unit, ensure that the evaporator connectors are not damaged.
- Check the position of the evaporator connecting flange - D -, it has to be flush with the housing of the A/C unit - A -.
- Check the connecting flange of the refrigerant lines - C - and the connecting flange at the evaporator - D - for contamination and damage.
- Assemble the connecting flange - C - (of the refrigerant lines) and the connecting flange - D - on the evaporator - E -.
- Install the screws - B - (tightening torque 10 Nm).
- Insulate the area at the evaporator connecting flange where you removed the insulation using a piece of self-adhesive thermal pad - A -.
• This thermal pad is available as a spare part.
- Fill the groove - B - in the lower section of the service cover - A - with silicone sealant D176 001 A3.
• The replacement service cover - A - comes with 7 screws - C -.
• If the A/C unit/service cover connection is not sealed, condensed water may enter the footwell from the A/C unit, such as when driving around curves.
- Install the service cover - A - on the A/C unit evaporator shaft.
- Reinstall all removed components in reverse order of removal except the lower instrument panel cover (driver's side), the glove compartment, and the plenum chamber cover.
• Connect the 2-pin harness connector to the Coolant Pump (V50) of the pump/valve unit only after bleeding the coolant circuit.
• The Coolant Pump (V50) (in the pump/valve unit) may only be operated after bleeding the coolant circuit.
• Dry running of pump in pump valve unit leads to destruction.
- Fill and bleed cooling circuit.
• 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 cause the customer to complain of insufficient heating performance in winter or different air temperature from vents at same setting in regulated mode
- After bleeding the cooling system, check it to ensure it is sealed tight. In particular, note the connections between the coolant pipes and the heat exchanger
- Check the position of the grommets in the coolant pipe feed through from the plenum chamber to the passenger area for proper seating.
- After installation, check the grommet between engine compartment and plenum chamber at the coolant hose - C - for proper seating.
- Check the pump/valve unit, it may not make contact with other components (noises).
- After bleeding the coolant circuit, connect the connectors - D - to the Left Heat Regulation Valve (N175) and Right Heat Regulation Valve (N176), and - E - to the coolant pump Coolant Pump (V50).
- Evacuate and re-charge refrigerant circuit.
- After filling the refrigerant circuit, check the refrigerant line connection points in the plenum chamber and evaporator for leaks, e.g. using an electronic leak detector.
- Clean coolant residue from the plenum chamber.
- Install the remaining removed components again in reverse order.
- Check the DTC memory for the Climatronic Control Module (J255) A/C control head and erase any faults displayed if necessary.
- Operate the A/C system after filling the refrigerant circuit => [ A/C System, Operating after Filling Refrigerant Circuit ] A/C System, Operating after Filling Refrigerant Circuit