AC not functioning correctly

[George Selby]

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