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Audi A6 C5: How to Clean Air Conditioning Evaporator Drain Valve

If you’ve noticed your A/C is not performing as well as it should, or a general dampness in the cabin of your car, chances are you need to clean out your evaporator drain valve.

By Jeffrey Bausch - April 8, 2016

This article applies to the Audi A6 C5 V6 (1998-2004).

An evaporate drain valve is specially designed to transport evaporated water to the outside of the car. Unfortunately, it can get clogged over time due to debris. When this happens, the A/C system will suffer, and there will also be a general dampness to the cabin of the car. Another way to confirm whether or not it needs to be cleaned is to check for water in the passenger side foot well.

Cleaning it is pretty straightforward and can be accomplished in about 30 minutes or so. Read on to learn how.

Audi A6 C5: How to Clean Air Conditioning Evaporator Drain Valve

Materials Needed

  • Screwdrivers (Phillips and flat head)
  • 1/4" drive ratchet
  • 1/4" u-joint
  • 1/4" extensions (a few different lengths)
  • 8mm socket
  • Compressed air machine

Step 1 – Remove the glove box

Simply locate the five 8mm bolts underneath and pull the box out. Two are on the outside–remove them, then open the box and remove the remaining three. Lower the box to the ground and locate the connector; remove it, then remove the glove box from the car.

AUDI A6 C5 C6 AIR CONDITIONING AC EVAPORATOR DRAIN EVAP VALVE TUBE CLEAN HOW TO
Figure 1. Glove box mounting screws.

Step 2 – Remove the side panel

Near the floor and in front of the passenger front door, remove the screw cover using a flat screwdriver; next, remove the two Phillips screws. Once they’re all out, pull the lower portion of the panel to the side. Loosen the door trim by pulling it up and back so that you can get to the drainage duct.

AUDI A6 C5 C6 AIR CONDITIONING AC EVAPORATOR DRAIN EVAP VALVE TUBE CLEAN HOW TO
Figure 2. Side trim panel clips.

Step 3 – Access the evaporator drainage valve

With the carpet out of the way, you should be able to see the drainage duct coming out of the center console. Remove the three bolts that are holding it in place. You can get to two of them with an extension and 8mm socket. The bolt in the back will require a u-joint to remove it. Once all the bolts are up, move the drainage duct up and you’ll have access to the evaporator drainage valve.

AUDI A6 C5 C6 AIR CONDITIONING AC EVAPORATOR DRAIN EVAP VALVE TUBE CLEAN HOW TO
Figure 3. Drain tube mounting bolts.

Step 4 – Clean the drainage valve and reassemble

Using an air compressor machine, blow out the valve with compressed air. About 50psi of sustained air pressure should do the trick.

When complete, place the drainage duct back down and secure with bolts. Place the carpet and trim back over the area and replace the side panel back into its original position. Put the screws back in. Bring the glove compartment back into the car and reconnect it to the connector. Snap back into place and put bolts back in. Tighten until secure.

AUDI A6 C5 C6 AIR CONDITIONING AC EVAPORATOR DRAIN EVAP VALVE TUBE CLEAN HOW TO
Figure 4. Blow compressed air through the tube.

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