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Old 05-11-2006, 07:01 PM   #1
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Default Heater core mini-write-up

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.

The new heater core superceeded by Audi will have smaller inlet/outlet than the original. This is not a problem, the hoses clamp down on the smaller diameter without any leaks.

The center and rear dash sections removed. 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 seperated from the airbox.

You may notice leaves all over the passenger side carpet. 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.

Testing position/temp flaps with VAG-Com.*

Disconnect the left/right footwell vents as well as the rubber center section from the airbox:

Driver side footwell duct... these just snap out:

Heater box out after all hoses disconnected. I used a few broom sticks to pry the box out.

Where the heater core lives:

Heater core inlet/outlet. I suspect this is where the leak was happening. Peel away the factory sealent with a screwdriver.

Airbox seperated, blower motor out. I should really replace the blower motor now, but I don't have one on hand. It's a good time to clean up and re-lube the rubber blower motor mounts, as well as cleaning up any dust and dirt.

Heater core removed:

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. I think C is for the earlier C4s. RTV 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.

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Old 05-11-2006, 07:54 PM   #2
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Default Dayum, that looks like a PITA. I respect your dedication.


Original S4/S6 FAQ>
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Old 05-11-2006, 08:04 PM   #3
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Default Nice work. For the benefit of anyone else doing this job...

The center console doesn't need to come out in order to pull the heater box. You can reach in to disconnect and reconnect the ducts and harnesses from the footwells with the console in place. It's kind of a PITA but quicker than removing the console. I'm sure having the console out made testing the flaps a lot easier though.

Brdman, I hope you avoided what happened to me: I took it all apart, replaced the blower motor and heater core, and put it back together, only to have the brand new blower start screeching a few minutes after it started up. Had to take it apart again and re-seat the motor. The good news is this job is really not that bad the second time you do it.
1994 S4 with stuff
1996 A6q Avant with no stuff
1990 Miata with a little stuff
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Old 05-11-2006, 09:37 PM   #4
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Default Kudos for figuring out how to split the box.

1990 Audi Coupe Quattro - Tornado Red
1990 Audi Coupe Quattro - Black
1992 Audi S4 - Cyclamen Pearl Effect
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Old 05-12-2006, 12:40 AM   #5
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Default 2nd - did my heater core replacement without removing anything more than the knee-panels from

the interior cabin. But I used an engine bridge to lift the airbox out as described in Bentley - which made it much easier.
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Old 05-12-2006, 03:29 AM   #6
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Default Where did you get an engine bridge?

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Old 05-12-2006, 06:04 AM   #7
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Default Looks like a big job! Congrats!

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Old 05-12-2006, 06:42 AM   #8
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Default Re: Heater core mini-write-up

I had a local fella here do the core in mine and he never even seen a Audi! But I think he fig out how to get it out from under the hood and I believe he did something like VR was saying about a bridge. I know for sure that he never got into the job that far!! He did tell me though that he did not want to do another one!!!!!

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Old 05-12-2006, 07:52 PM   #9
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Default Way to Go! You have my total respect for doing this job. Long live your Audi.

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Old 05-12-2006, 09:35 PM   #10
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Default How long did it take to get everything apart? How do you remove the council around the e-brake?

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Old 05-12-2006, 09:35 PM
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1996, 225, 431, 819, a4, audi, b6, c4, core, drivers, flap, heater, motor, s4, seal, servo

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