1977 GMC C25 A/C compressor clutch wiring


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Old 07-18-16, 05:54 PM
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1977 GMC C25 A/C compressor clutch wiring

I inherited a 77 gmc sierra classic. the motor has been swapped. had a 454 now has a 350. while trying to get the AC to work I was tracing the wire that supplies power to the compressor clutch. I found that it terminates after the connector that is attached to the back of the hood. I'm not the most Mechanically inclined person but I'd like to re wire it. my question is. where is the power wire (green with single white stripe) supposed to go? a switch I'm assuming. I just need to know what it looks like. Thank you all.

Edit: Meant to put 1977 in title not 1077. won't let me edit it.
 

Last edited by Erik Lucero; 07-18-16 at 05:56 PM. Reason: misspelling
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Old 07-18-16, 06:28 PM
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Been years since I worked on one, Trying to remember the wiring for your truck. There may be a pressure switch mounted near the evaporator. If not one there it may go to the switch in the dash. Should be a wiring harness that goes through the firewall where the rest of wire is. But like I said has been many years since I have even seen one. Tried to find a wiring diagram at autozone but had no luck. You might be able to find a repair manual at local library. Remember that is a r12 system and it is very expensive.
 
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Old 07-18-16, 07:23 PM
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I edited the title for you.

At Autozone.... this is the closest diagram I could find for you.

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Old 07-18-16, 07:41 PM
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Thank you guys for your replies. I took some pics but it won't let me upload them. I'll try to upload them when I get home. It's been converted to a 134. Running a wire is easy, I just don't know what the switch it's supposed to go to looks like.
 
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Old 07-18-16, 07:53 PM
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Phone pics are too large to post directly here.... http://www.doityourself.com/forum/el...-pictures.html
 
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Old 07-18-16, 08:18 PM
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it comes off the compressor and goes to what is pictured in the second picture. it goes into the harness. (I haven't dug into the harness I'm working had to take pics on my lunch.) same color comes out by what is in the first picture. it that the switch I need to wire to? And thanks PJMax for all your help.
 
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Old 07-18-16, 08:35 PM
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This device is a like a thermostat. It monitors the evaporator coil temperature and cycles the compressor to keep it from freezing.

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So the flow of power is +12v thru the A/C selector on the dash ----> thru the wiring harness to that plug coming out of the harness ----> to that cycling thermostat ----> to the clutch.

Do you have the engine in and running ?
Applying 12v+ to the plug coming out of the harness should activate the clutch. If you try that.... unplug it from the harness first.
 
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Old 07-18-16, 09:18 PM
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I'll have to get to it in the morning. will post an update as soon as I can try it. Thank you everyone for all your knowledge and help.
 
 

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