A/C Fun

I lost cold air in my A/C several weeks ago. For all I know it has never had an ac service, could have been the same 134a in it for the past 18 years...? Anyway, I hooked up a manifold set and the low side read about 15 psi, high was way under 50. Outdoor ambient temp was maybe 75 F or so. Even with the ac off, the low side stayed very low psi reading. While keeping it all running, I closed the high port, closed and removed the low port, and added some gas. Stopped, checked it, a tad under 20 (high around 150), repeat. The compressor started squealing a little at low RPMs. If I revved the engine the squeal would stop. Air became cold again, and the low reading was just under 30 psi. I repeated again until the low was just under 35 and the high about 175. But the compressor has a constant squeaky squeal in low RPMs as long as the ac is on. If I turn the ac off the squeal goes away. I get the RPMs over 2k and the squeal goes away. With the system off the low psi jumps to over 70, which I think is normal.

So what's with the squeal? I am fairly sure my belts are a tad loose, so I need to tighten them. Would a loose belt cause that, only when the system has pressure and on? I do not get the squeal when ac is off, and did not get it when it was on blowing warm air when the refrig was too low. Air in the system?

 

Sounds like the belt is just a little loose. When you had less freon, the compressor wasn't working as hard, so the belt wasn't slipping. Now that there is more pressure, the belt is slipping. Try tightening the belt just a little and see if it solves the problem. If the belt is old and cracked, replace it.

 

The belts are new, but I have not tightened them very well. I think this is the last one that needs some cinching up, so I will give it a try.