Well, we're working on my A/C after having taken it apart for the engine rebuild last winter. Just now getting around to recharging it.

The compressor will kick on and start to cool, but the pressure side jumps up to 400 psi very quickly, then of course shuts the compressor's clutch down.

The low side pressure seems to be OK. Low side and high side both equalize once the compressor/engine is shut down. So it seems like there are no leaks, and everything looks to be hooked up correctly.

What could be going wrong here?

TIA for any help.

 

Sounds like you have air in the system.
Did you Pull a vacume on it before you charged it?

 

Yep, 30 in/hg for about 5 minutes....and it held for a few minutes after that too before we started filling it with freon.

 

Sounds like a partial blockage before/in the evaporator. Does it cool REALLY well or just so-so?

This is from my experience working on refridgerators, not car AC. Same principles though.

 

That's what we were kind of thinking it was as well. The guy who is helping me says it seems like it's in the area of the condenser, and not at the evaporator. It only cools so so, not as cold as it should be.

I just am not sure what could be blocking it. Nothing got into the condenser that I know of, or the compressor, or any of the lines, for that matter.

 

The reason I mentioned the evaporator is

A. Because you are experiencing problems in the high pressure side and not the low pressure side.

B. There is a venturi on the evaporator side that assists with freon evaporation. Having this partially plugged would do exactly as you described. It only takes a well-placed piece of dust or dirt (or water in the system which has frozen) to cause this.

If that's the problem then it would seem to me that you could disconnect the condenser and compressor and "reverse flush" the system with nitrogen.