I just put new compressor and dryer on R-12 ac system. Ive had no air for 2 yrs now so fearing moisture may be in system I pulled vacuum down to 29 and let it run for a hour.Closed valves shut off pump and watched gauge. System held vacuum perfectly. I opened valves cut on vacuum and ran pump 3 more hrs. Closed valves cut off pump removed it. I connected the Freon can and with high side valve closed opened low side to charge system. After 45 min can was only half empty and low pressure gauge was up to 85-90. I tried jumping the pressure valve so pump would run and it would cycle but seemed under a lot of pressure (hard for belt to turn pump) It would run then belt slip then run and engine would pull down and shut off. I let truck sit overnight and tried it the next morning and it did the same thing. Low side up to 90. The new compressor i put 6.5 oz of oil and 2 oz in the new dryer. I put the new orifice filter inline on the high pressure hose. What can the problem be a bad compressor? . Please any help is appreciated. Thanks Big Nick

Rule of thumb on oil for a compressor is, empty oil from old compressor, into a measuring cup......if less than 2 oz, add 2 oz to new compressor.....if more than 2 oz, add the same amount to the new compressor.....

One thing you can do, is grab the clutch plate and try to manually rotate it by hand......it should rotate....

What is the high side pressure doing?

Why was the original compressor replaced?

The clutch plate would not rotate without help of huge channel locks when I first put oil in it. I just went out and tried it now and the compressor and clutch plate turns my hand. I put 6.5 oz oil in new comp. 2oz in dryer along with new orfice tube filter. Old compressor cooled fine just wouldn't leaked around big gasket in compressor. The old Fully charged system cooled about 4 months then leaked down. I checked for oil in old compressor and found very little at all. Old compressor leaked freon that'* why I replaced it. The high side gauge slowly started to go up after trying to add freon for over an hour in new compressor. Could the compressor be bad? What to do next? Thanks for helping me I appreciate it. big nick









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I would guess that you have more oil in the system than specified, but it wouldn't concern me, IMHO.
How did the old orifice tube look?
Unfortunately, I will assume this is an R4 compressor, which wasn't the greatest new from GM. The new, aftermarket compressors (GM got rid of the tooling years ago) are even worse.
I managed to find a genuine Delphi service compressor when I needed one for my Caprice. The front shaft is easy to replace with the improved, double lip seal, but I sprung a body leak (like I believe you described), which I don't think are readily repaired (from what I have seen).

ORIFICE TUBE FILTER HAD A SMALL PIECE OF THREAD IN IT THATS ALL.

Since you vacuumed the system, and I assume charged into the vacuum, it is sounding like a bad compressor to me (unfortunately).

If the high and low pressures are very close to eachother when the compressor is running, there is either an issue with the compressor or expansion valve.

Yes, an orifice tube that broke right away would do that. I've had some off shore ones recently that seemed more fragile.