brown7373

I need to replace the A/C compressor on my 72 Cutlass Supreme Convertible. I have been seeing with or without Superheat, supposedly something on the back of the compressor.

Should I have that compressor or not? How do I tell if my car originally had it? What does it do? Can I use a superheat compressor if it didn't come that way originally? Are there any pluses or minuses? My system has been converted to R134a and has a new POA calibrated for 134a and has a new crossflow condensor designed for 134a.

MDchanic

The Superheat switch was a primitive pressure safety switch designed to cause a fuse to blow if the freon level got too low. It's a weird system, and not very good.
Most modern owners, who are treating their cars well and paying attention to them, would not run their compressors if the juice was low, so under current conditions, it's an absolutely useless feature, and one you'd probably disable if it ever kicked in.

I believe all '72's had this, but you can tell by looking at your wiring - superheat has 2 wires going to the compressor - 1 green and black, with a black ground wire, going to the two spade terminals of the clutch, and one black with a rubber boot, going to the superheat switch pin terminal on the back.

- Eric

brown7373

Thanks Eric,

I didn't see any wires at the back, but with a 39 year old car, obviously things have been changed. It is not now or ever going to be a perfect car, so unless there is some reason to use the superheat, I am going to avoid it.

Lady72nRob71

The 72's used the superheat switch as standard. Function is as mentioned already.
The fuse was actually a thermal delay fuse that clipped on the compressor frame - 3 terminal black thingie.
Most AC systems have some sort of low freon cutout switch and providing the system was charged correctly, the SH switch causes no real issue.

If you want originality, get the one with the SH switch.