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'84 5k A/C controller curiosity
>Date: Tue, 1 Sep 1998 13:33:33 -0400 (EDT)
>From: "G. Benedikt Rochow" <firstname.lastname@example.org>
>Subject: '84 5k A/C controller curiosity; also Pentosin
>Has anyone here ever taken the climate control controller apart to
>see what sorts of electronics are inside?
>I'm just wondering whether it's just a few standard
>logic chips (as it should be - it doesn't do that much),
>or some impossible-to-replace custom logic or microcontroller
>(I'd rather ask now, before it fails stuck at full-cold
>in the middle of the winter...)
Not much inside. Usual problem is the solenoids get oil in them (runs up
the vacuum lines) and the rubber seals swell. Quick test - remove
controller box, remove PC board, shake - if it rattles, it is OK. No rattle
means swollen seal, that solenoid is bad. Note that EACH solenoid must rattle.
The little vacuum distributor disc also has a rubber one-way valve in it -
also usually swollen shut - blow through it - no air means no good.
Of course, you can't buy the individual solenoids from Audi. Visit a
u-pull-it junkyard - this is a GM part - found in GM large cars
(Cad-Olds-Buick) of 1990-ish vintage - entire controller box costs $10
there. Take it apart, unsolder good (rattly) solenoid from GM board, solder
it into Audi board.
Other things to check - cold solder joints on solenoid to PC trace
junction, stripped gears in motor (use the GM motor - make sure you index
the little actuator arm before you pull it off).
Save the disc-shaped vacuum distributor, too - you'll need it.
Failure modes: Only defrost works - no air from center vents - solenoids.
Clicking or ticking from programmer box when temperature changes - motor
and gears (the gears are plastic and strip easily.)
There are usually other problems here as well - fresh air recirculator flap
arm is often broken - remove plastic panel over A/C and wiper motor, reach
in and wiggle recirc door (this is on the pass side of car) by hand - if it
flops easily, the arm is broken. Repair part available from Audi or from
parts car, major PITA to get to - mostly tough to reach - skinned knuckles
For a while, I considered fixing programmer boxes "on the side" - the total
lack of response led me to believe I should keep my day job . . . so I'm
now giving away what I can't sell (no nasty comments, please - you know who
you are . . .) <G>