AC not functioning correctly

[walian at att.net]

George,


  I have had simular problem on some former 5000s. The problem ended up being
the high pressure switch. When the pressure gets to low it turns off the
compressor so the system doesn't freeze up. The switch on my 5000(s) was
located on top of the fire wall passenger side where the line runs into the
car ( under the plastic cover by the windshield wipers) . The problem ended
up being the switch on 2 of my cars. I temporarily just jumper-ed the
connection and it worked fine. I  don't recall if the audi ac has a view port
for the freon in the dryer but I was told if you see a bubly fluid in the
view port when the compressor is running it generally means the system is low
on freon. I would look at this first and then jumper the high pressure switch
to see if this is solves the problem. You should probably take a measure on
the switch but if it is intermittent you won't really be able to tell by
taking one measurement. From what I recall the switch is Normally Closed
therefore I actually shorted out the two wires.

Frank
> Up until this past Wednesday, the AC in my Audi 80 worked fine, with temps
> coming out the vent of 40 degrees F.  All of a sudden on Wednesday, I
> noticed the air was a lot warmer.  I put the thermometer back in the dash
> vent, and the vent temps are all of a sudden 60 degrees F.  Another strange
> symptom is the air warms up as you drive, and it gets colder while you sit
> at a light.
>
> I started paying attention to the AC compressor cycling, and have come the
> conclusion that the compressor isn't staying on long enough.  When sitting
> at a light, it stays on about 30-40% of the time, but while driving it only
> stays on for about 5-10% of the time, it comes on for a second or two, and
> then clicks off.  I jumped the relay (you can hear it click each time the
> compressor cycles) but the compressor STILL cut out at the same
> frequency.  So I need to know what controls are in between the relay and
> the compressor (like excess high side pressure sensor, or the like) and

> where they might be located.  Car is a 4 cyl./2wd.
>
> George Selby
> 83 Audi Coupe GT
> 89 Audi 80
> gselby4x4 at earthlink.net
>