Don81

I am replacing the A/C compressor on an 81, and a question I was presented with at the parts house was, did I need the switched or non-switched a/c compressor.

1) What is the switch for that is built into the compressor? Is it going to be a pressure safety switch?

2) Is that same built in switch the same as the pressure switch with the harness next to the evaporator core? If so can I bypass the pressure safety switch next to the evaporator core?

3) I was given the only compressor they had in stock and the guy said it is the switched type. Was this the kind that came on the 81 originally? Will the switched compressor work?

4) It being a new compressor, will I have to add oil to it? If so what oil type do I add? It was converted to R134 already when I bought the car.

markdtn

The switch is the superheat switch on the back of the compressor. You either have it or you don't. All new compressors are shipped dry so you need to add oil. I'm not sure how much, but the parts store should be able to tell you. They will probably recommend PAG oil. If you replace the compressor you should also replace the accumulator and the orfice tube.

mikejpss

I am unsure of the "switch" you refer to. Is it a Hi pressure switch? if so, the 81 isn't wired for that-jump it out.
Oil: You will easier find a needle in a haystack b4 you find someone in the auto parts industry that will tell you the correct amount of oil to add in the system.
IF you were able to drain oil from the old compressor, add that same amount of new oil (compatable with 134a) back into the new compressor.
If the old compressor was dry (often times) , I would add 4 ounces new oil into the new compressor.
Change the accumulator and orifice is a good suggestion.

Don81

Yes, after doing research, I came to the conclusion that it is a high pressure switch. There are no extra wires that go to it. It's just a plug with a "C-clip" that the other compressor didn't have. I read somewhere that when doing a R134 retro, it is required by law to install a high pressure switch in the system.

Would it be correct to say then that the compressor that I was given with the high pressure switch is what I should go to?

I'm also assuming that the other switch near the evaporator core is the low pressure switch and I do not bypass it.

noonie

R4 I presume. That awitch usually interrupts the ground to the clutch. If your wiring dosn't accomodate it, then just ignore the switch.
To be legal with a 134 retro, you must add a separate high pressure switch.