A/C Low Pressure Switch Problem

[86GNER]

The compressor on my 86 GN does not go on unless I jiggle the connector going to the Low Pressure Switch (Pressure Cycling Switch) on the accumulator. I tried to bend the male prongs out a little on the switch attached to the accumulator and I also tried to bend the female prongs in the harness that attaches to it. It works for about 5 minutes (The compressor goes on) but then turns off again after driving a few miles. Jiggling or disconnecting and reconnecting the harness turns it back on momentarily but the compressor shuts off again after a few miles of driving. I tested the freon level and it is correct. I assume I have a bad pressure switch or harness/connector. I know that A/C Delco makes the low pressure switch that attaches to the accumulator. However, does anyone know where I can get a NOS harness or aftermarket harness that looks stock? I would like to replace both but cant find the harness.
Also, I have noticed that some of the photos in the service manual (SEE Page 8A-201-17 of the GM Service Manual) show the harness (female) as being the pressure cycling switch. It actually has an arrow pointing to the harness instead of the switch attached to the accumulator. Am I correct in assuming that the arrow in the manual was supposed to be pointing to the switch (male prongs) on the accumulator as opposed to the harness that connects to the male prongs? In essence, I want to know if the harness is the pressure cylcling switch or if the pressure cycling switch is located on the accumulator.
Finally, is there a way to tell if it's the harness that's bad or the switch? I know people talk about "jumping" connections but I dont know exactly how to do it. Any basic articles on this for a novice? Thanks for the help.

 

[Roc87]

To "jump" the connection or harness, you can either use a paperclip, or make your own using a small piece of wire and two spade connectors crimped onto it. From what you describe, it sounds like the connections are not conducting current correctly. Are the terminals dirty or corroded? Try scraping the male terminals on the switch with something like a razor blade, and maybe a very small screw driver to clean the terminals inside the harness. If you do end up replacing the pressure switch, there is a schrader valve inside, so you shouldn't lose too much coolant. I rather doubt that they have the harness new, but I would think nearly any GM vehicle in the junkyard will have the same pressure switch harness, or just attach some female spade connectors on your factory harness (although it won't look "factory", it will still function)

 

[86GNER]

How would I determine if the switch is bad? I have read a forum post where someone jumped the pigtail (harness) to see if a new Harness they installed was good. How would I go about doing this?

I have looked at so many websites that sell replacement connectors/harnesses. Unfortunately, the one they dont seem to make is for the low pressure switch. They make it for the high pressure but not the low. Go figure.

 

[Roc87]

With the car running, and A/C turned on (with a jumper in the harness) use a multimeter on the connections to the pressure switch. On the Ohm setting, there should be a nearly zero resistance, as all that switch does is complete a circuit.