AC problem

[oldasrocks]

I have a 96 GMC Van with AC leaks. I've had it filled many times and added stop leak. Changed the compressor and coil. Looked with the special glasses and UV light and cannot find a leak anywhere. When filled it vacuums down and holds fine.

Any idea where the fluid is going?

[Travis in Louisiana]

How fast does it leak down? Did you change the Condenser coil in the front of the truck, or did you change the evaporator coil under the dash in the truck? If I remember right, most GM vehicle A/C's leaked a small amount from the seal in front of the compressor, very small. When the system is running, the evaporator coil is a low pressure, say around 35 lbs. The condenser coil is high pressure, usually around 250 lbs. or more if memory serves me right. There are o-rings is the connections where the lines bolt together. If you brerak any of these lines in repairing the A/C, you will need to put new o-rings, which I think you probably did. I would say you are getting a leak with the A/C running, from some part on the high pressure side, that is expanding after the pressure builds up. I have also had the evaporator coil leak more after the A/C is off, than when running. With the A/C off, the pressure in the system equalizes, thus bring the evaporator coil pressure higher thatn the 35 lbs. The freon is going somewhere. Evaporator coil leaks are hard to find. I think we used to stick the leak detector probe into the drain hose of the evaporator coil casing to detect the leak, usually with the A/C off. Hope some of this helps.