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How to Remove and Replace the Heater Core (Matrix) in a '92 '98 Audi C4 (100/A6/ S4/S6 )

from wikiHow - The How to Manual That You Can Edit
This article may need to be cleaned up to meet wikiHow's quality standards. You can help by improving it and removing this notice when complete. Notice added on 2008-01-12. The following is my experience with a '98 A6q Avant. The entire C4 lineup should be the same. Have a digital camera handy to document disassembly. A Bentley Manual is essential for reference, as this article does not document all details.

Steps

1. Remove The center and rear dash sections. The entire dash does not need to come out. Simply remove the center consoles, the driver side lower panel, and the glovebox. This will expose the ducts that need to be separated from the airbox.
2. If you have a VAG-Com tool, now would be a good time to check if your blower motor and various temp/position flaps are functioning. Go to the HVAC control section of the VAG-Com software and run a full test. You should hear the various flaps and motors working.
3. You may notice debris on the passenger side carpet once the glove box comes out.
4. These came from the recirculation flap located above glovebox. Now is a great time to clean it out. Open the flap by hand and clean out any debris. Mine was clogged full of leaves and Kleenex.
5. Disconnect the left/right footwell vents as well as the rubber center section from the airbox.
6. Driver side footwell duct. these just snap out.
7. Now that the heater box is free from the interior ducting, it can be removed. I used a few broom sticks to slowly pry the box out. Be sure to remove all wiring, vac lines, and the large hose clamp holding the rubber sleeve on.
8. The heater core is located inside this box. Remove all the screws and clips. Many screws are hidden, so be careful, and don't force anything.
9. This is the heater core inlet/outlet. Remove all the sealent before removing the core. Use 100% silicone when re-sealing the new core.
10. Heater box disassembled. Clean it out before reassembly. Now would be a great time to replace the blower motor. These fail often, and you don't want to repeat this job.
11. Old heater core out. Re-assemble. See note warnings section.

Tips

• For re-assembly, purchase a new airbox seal, part number 431 819 225. Should be around $10. For reference, the heater core part number is 443 819 030 (D or C) D has a larger inlet/outlet, but Audi has replaced all parts with the smaller inlet/outlet model. 100% silicone can be used to reseal the heater core into the box.
• All temp/position flaps use the same servo motors. Worlpac sites only list one flap motor, but it can be adapted for use in all temp/position applications. Make sure the red/blue motors connected to the heater box are fully operational before re-assembly. Pulling the fault codes from the climate control will help diagnose any problems.

Warnings

• Do at your own risk

Things You'll Need

• Assortment of metric hand tools
• New airbox seal
• Heater core 443 819 030
• Seal 431 819 225
• Audiworld.com forums
• Optional: Vag-Com
• Optional: New blower motor.

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