Ok so first off I am not entirely new to A/C issues and knowing how to solve and repair the issues. But I unfortunately have never came across this problem I am currently having. I just recently bought a 2004 Suburban. Within the first few hours of owning it I noticed if I let the suburban idle for more that 5 min or so it would heat up to around 220 and the A/C would start blowing cold, but then as soon as I would start driving the coolant temp would return to normal and the AC would begin to freeze you out again. So naturally I bought a new clutch for the fan. The new clutch solved the heating up issue at an idle, but the A/C would still get warm within a minute or so of coming to a stop. So next I cleaned out the condenser coils to make sure it had proper air flow but it still didn’t help. I hooked up my gauges this evening to find the low side siting at over 90psi and the high side at 400psi! My first thought after finding this was to slowly drain some of the Freon to get the pressures down to the correct psi for the ambient temp outside “it was 110 today”. I ended up draining about 10psi to much out so I added a little back and got my low side about 55psi but now high side is only sitting about 250psi which I’m pretty sure is low for the high side now, and the vehicle is blowing I would say high 70 degree air no matter if it’s at idle or running down the highway, and also now you can feel the compressor kicking In and out at highway speeds, but it is NOT kicking in and out at idle. Does anyone have any thoughts? I apologize for the long drawn out story. Thank you in advance.

 

My guess is the A/C compressor has been damaged do to the very high pressures. 400 PSI is _WAY_ past the 300 PSI mark, which is high-normal and 90 PSI is also far and away above what is normal for the low-side pressures, as well. 70 F is not even close to the 38-42 F range it should be running at, if it were running normally.

 

Sorry, but the only way to determine refrigerant charge is to have it pulled out and weighed. And the right way to add it as well: by weight.

The fan clutch idea was a decent guess. One typically confirms a condenser issue by spraying the condenser with water and see if pressures drop considerably.