96 Passat TDI A/C not working all the time

Hello,
My A/C is not working all of the time. It seems that when it is really hot it won't come on and as the car cools a bit it works. I found a thread that talks about a similar issue on a newer Passat. They mentioned that a bad relay was probably the cause. I am thinking that I may have the same issue. Where are the A/C temp control relays in my car? Or, are there any suggestions as to what the problem might be? I have ruled out low freon because when the A/C works it is good and cold.
Thanks,
Deb

Are BOTH the radiator cooling fans working?

Does the AC cool better on the freeway?

Tony

You could have:

A weak compressor (these are variable-displacement, so they can intermittantly stick in the lesser-displacement mode)

A sticking expansion valve

A flakey pressure switch on the drier

Incorrect refrigerant charge

You would really need to connect gauges to the system to see what is actually happening.

The relay on the B5 Passat is not at all the same as your car.

What I would do first is check to make sure both fans are spinning. The first fan has the motor, the second fan is driven off the first via a tiny belt.

Next make sure the compressor clutch stays engaged the WHOLE TIME the system is on. These compressors do not cycle on and off, as they are variable.

If all that checks out, gauges are pretty much the only thing left to use for checking.

This probably should be a new thread, but it seemed some sharp people were responding to this one, and it is related. I looked at the exploded diagram of this compressor (SD7V16) and couldn't see how this variation in the displacement is accomplished. How is this done? Anyone ever taken one appart and figured it out?

Chuck