I am ready to replace the old High and Low pressure connectors. After, reading the previous info about these switches and their connectors. I know that each connector connects to one high and one low wire. The other wire on each connector must be ground.
My question is: Has anyone found a neat or correct way to ground these two wires?? Should they be ground to the frame, the starter ( that is real close) or to something else???

quote Originally posted by 86 Vintage Fiero: I am ready to replace the old High and Low pressure connectors. After, reading the previous info about these switches and their connectors. I know that each connector connects to one high and one low wire. The other wire on each connector must be ground. My question is: Has anyone found a neat or correct way to ground these two wires?? Should they be ground to the frame, the starter ( that is real close) or to something else???

I don't know if you got an answer on this but I tested this out prior to permanently grounding out the wires. I got the compressor installed and turned ignition to ON but without starting it and left A/C turned OFF. I grounded the high pressure switch pigtail against the back mounting plate screw, and inserted the other pigtail into the factory high pressure switch and it kept kicking the fan on. So I cut the high pressure switch pigtail short and I'm going to leave the grounded side DISCONNECTED.

quote Originally posted by sricka01: I don't know if you got an answer on this but I tested this out prior to permanently grounding out the wires. I got the compressor installed and turned ignition to ON but without starting it and left A/C turned OFF. I grounded the high pressure switch pigtail against the back mounting plate screw, and inserted the other pigtail into the factory high pressure switch and it kept kicking the fan on. So I cut the high pressure switch pigtail short and I'm going to leave the grounded side DISCONNECTED.

I had heard about some people having this problem as well but when I hooked mine up I just grounded the two grounds for the switches to the engine and mine works correctly.
My is an 88 and I don`t know if it`s different on other years or not.

quote Originally posted by TXGOOD: I had heard about some people having this problem as well but when I hooked mine up I just grounded the two grounds for the switches to the engine and mine works correctly. My is an 88 and I don`t know if it`s different on other years or not.

This is really odd because mine is 88 GT. So why are these SANTECH MT0671/0678 combination switches giving different results?

quote Originally posted by sricka01: This is really odd because mine is 88 GT. So why are these SANTECH MT0671/0678 combination switches giving different results?

I`m not sure.
I was fully prepared to leave my grounds disconnected but when I hooked them up it worked so I left it.
I think mine were the same switches.

I attempted to charge my A/C and the compressor won't engage. I tried paperclip in the front pressure switch but all that did was raise the idle speed. Is it because I didn't ground out the high pressure switch? I don't friggin understand why some Fiero's the fan doesnt run constantly yet mine is one that does. What gives?

RWDPLZ - thanks for being patient.

Okay so I solved my Santech A/C switch wiring problem in case this ever gets archived. And I think this has screwed up others along the way too. Santech, now makes the purple switch BLACK for MT0671. That confused me somehow. Now that I've reviewed it again, it's quite easy to get confused when underneath the car trying to get it all put together from memory. The fan wire is nothing more than a ground circuit going to the purple/black switch. If the fan runs while key is ON and A/C is OFF, it's most definitely wired to the wrong switch.

I can't remember which, but one of the new switch pigtails is red. I installed the new switches based exactly on the old orientation. And after installing it, the rotation is a bit off from where I memorized it. And since the old switch is red, it must have confused me so I hooked up the fan to the high pressure switch. And since that HP switch is always grounded the fan will always be grounded to RUN. After swapping the fan wire back to the right LoPres switch, I no longer have a problem. I also had enough pig tail to connect it to ground.

A prior thread https://www.fiero.nl/forum/Forum2/HTML/117640.html talked about how the old switches were white and red.

Purple/black switch is fan
Blue High Pressure (always grounded) is to complete safety ground for clutch to kick on.