AC quits working when the car stops moving?

[Andrew <aos+yahoo@xxxx>]

Hi list. I've been working on diagnosing an AC problem for a long time,
and I'm making no progress. Since summer is arriving again here in
Houston, I really need to get this fixed or I won't be able to drive the D
until winter. What fun is that? :)

My AC will cool for maybe 10-15 minutes at a time, and then quits cooling
and won't cool again until it's been left off for 30 minutes or so, at
which point it'll cool again for maybe 5 minutes. It won't get back to
being able to cool for the 10-15 minutes unless it's left off for a number
of hours.

Most interesting about this problem is that the AC always seems to fail
shortly after the car has stopped moving quickly. If I'm cruising on the
highway, the AC seems to work for a long time (although it *will*
eventually stop), but once I get caught in traffic (where the AC is needed
most, of course!) it quits cooling. If I hit traffic and it stops
cooling, then get moving again, it will resume cooling for a short period,
but stops again pretty quickly.

The only things that occur to me that change when I get caught in traffic
is airflow through the condenser is reduced and so is voltage throughout
the electrical system (which of course additionally reduces condenser
airflow due to lowered fan speed). Both fans are working, however, so
this really shouldn't cause the AC to stop cooling completely.

I do not appear to be leaking refrigerant anywhere.

I'm going to spend tomorrow evening with a friend of mine who has all the
appropriate diagnostic equipment, but I figured it might help for me to go
armed with some ideas. This is a pretty strange AC problem, and so far my
friend and I are at a loss to diagnose it. Any tips you guys have for
things for us to look at tomorrow night would be greatly appreciated.

-andrew
#4115
Houston TX