Automatic Climate Conrol...Audi 100...1990

[Mike Arman]

The climate control solenoids are the same as 90s vintage big-bodied Oldsmobile (and I think Caddie 
with the same body) but the case and mountings are not.


The solenoids often develop cold solder joints on the PC board, they should all be touched with a 
pencil iron and reflowed. The solenoids have rubber valves inside, you can tell if they are good or 
not by blowing on the tubes, I don't remember if you should get flow or no flow with the power off, 
but they should all be the same. If you get flow with power off, you should get no flow with power 
on, or vice versa. Powering the solenoid makes a difference.


The solenoids have small, square foam filters on them, by now these are all crumbled to dust, so 
make sure all that dust is NOT inside anything - that may clog the internal valves. I'd suggest 
taking apart a known bad valve so you can see how they are made, and that will enable you to fix the 
others.


Other problems are dried and split hoses, and there is a one-way valve in the box that sometimes 
clogs open. I've also seen the little air filter broken open. The gears on the motor can strip, the 
GM motor/gear train will work properly with a little parts swapping.


No idea why the fan runs with the CC box out - that might be a separate issue, but I think the CC 
box has some control electronics in it for the blower fan. Note that early (84-86) and later (87 and 
up) CC boxes are mechanically different but electrically similar (vacuum lines and valves) and of 
course they won't interchange.


Best Regards,

Mike Arman

90V8Q