Can someone please explain the function of the two pressure switches located on the AC compressor of my 87Gt? I have them out and want to replace them, but am not sure what pressure values they have. Also, one is open at 0 pressure, the other is closed. Is this correct or is one switch bad? If so, which one?
Thanks,
Daryl

One is the high pressure switch, the other is the low pressure switch. They are both sensing the same area of the compressor. Doesn't matter which port they're installed in, just as long as the correct harness wire is connected to it. The original style pressure switches aren't available any longer. You will have to replace them with a 2-lead pressure switch, of which one wire of each will need to be grounded. The old switches were grounded through the body of the switch. Newer switches have that extra wire.

So which of my switches is bad? Do you know the pressure specs of the switches? Also how do I know which is which?

I don't know the pressure values. The original switches had different harness connections, so they couldn't be crossed. The new pressure switches are color coded. One of mine was red, the other white. When you purchase them, they will be identified as to which is which. The pigtails on the new switches don't have terminal ends. They're just bare wire ends.

I'm not sure, but I think my installer purchased switches that were specified for R134a, so I suppose they're specific to the refrigerant. If you haven't done so already, you should also replace the cycle switch on the accumulator for one rated for R134a pressures if that's the refrigerant you're using.

There are a couple of other current AC threads. One of them has a number of charts that may provide some of the information you're seeking.

[This message has been edited by fierofool (edited 09-25-2018).]

Thanks! I just ordered the switches and connectors. Just recently bought this 87 GT. It was already converted, but poorly. Had sludge the consistency of peanut butter in the orifus. Needless to say, it didn't work. Your info is very helpful. Thanks again. Daryl

This is the thread I referred to previously. It may be of some help.
https://www.fiero.nl/forum/Forum2/HTML/000652.html