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wiring help...

jdmaffeo on Tue February 10, 2009 5:22 PM User is offline

Year: 1984
Make: Chevrolet
Model: C-10
Engine Size: 305
Refrigerant Type: 134a

I have converted my 1984 Chevrolet C-10 from the multiple belt setup to the serpentine belt setup from a 1992 Firebird. The newer style compressor needs to be wired up correctly. The truck setup has the pressure switch located at the receiver/drier. The new compressor has an extra sensor located on the back side (round in shape). Does the round plug need to be hooked up to anything since the truck pressure switch is currently hooked up still? I have one of the wires going to the compressor grounded and another one is 12V when the a/c is turned on. The compressor is cycling on and off. This is not normal from what I know of compressors. Any help would be appreciated! Thanks!! Jonathan

Chick on Tue February 10, 2009 7:10 PM User is offlineView users profile

Not sure about grounding the wire and 12v to the other? Anyway, the switch on the back of the compressor is a high pressor cutout switch, you can use them either way, if the old set up didn't have a switch, then don't hook anything up to the new one.. It won't cause any harm, but if you had one on the old one, and the new one didn't, then it could be a problem.. Use the cycling switch as it was intended, however, EPA laws to require a high pressure cutout switch on retrofitted vehicles. you can check out for the proper switches..Thats the easiest way in my opinion, just leave the switch off the rear of the compressor, as if it wasn't there.....Hope this helps..

Email: Chick


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mk378 on Wed February 11, 2009 10:21 AM User is offline

It's supposed to cycle to some degree especially in cool weather. Have you measured the refrigerant pressures? Was the system properly evacuated and charged after replacing the compressor? Has the accumulator / drier ever been replaced?

You might be able to use the rear high pressure switch by connecting the "cold" wire of the clutch coil to the switch instead of directly to ground. I think those switches are normally closed to ground. So in case of an overpressure the switch would open and the compressor stops.

GM Tech on Wed February 11, 2009 1:42 PM User is offline

The HPCO switches of '92 vintage are definitely two terminal normally closed---so you can wire it to whatever you want- to ground or to the hot terminal of the compressor- it is a switch- so you can use it to your advantage..

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

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