I have a 2003 Chevy avalanche, I have dealt with a not working ac for a while now. Last year I dealt with incorrect tension and after I broke 3 belts, I didn’t mess with it the rest of the summer. However before the belt broke the ac would work. After the first 90 degree day this year I decided I needed to fix it. I got that problem fixed, however this year it seems to have developed a new problem too. The pump will turn on when the ac is first turned on, then after a few seconds it will turn off. I connected a gauge to the low side port and when the ac is off the pressure is way higher than it’s supposed to be (about 65 psi) and I can’t fill it up anymore with my can. However when the ac turn on it drops down to about 15 psi then shuts off and stays off. I was seeing others having problems with it switching on and off continually but mine just stays off once it switches off. Any idea what could be causing this?

 

It takes a lot to bust a serpentine belt. Also, 65 PSI is a bit low at a static state (engine off) That said, without any high-side gauge information, my guess would be three things, assuming that the compressor and the magnetic clutch is working properly which, might be an issue as well:

1. You have air in the system.

2. You have an R134A "freon" leak.

3. Your system is plugged up, likely at the orifice tube.

You may also have a bad low-pressure sending unit as well.