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Old 06-21-2004, 10:47 PM   #1
Chevyguy111786
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help on Stock A/C on a 78 Big 10

I just bought a 78 Big 10. The big block was removed and replaced with a 305. It still has the stock components and i'm in the process of converting to 134a. Does anyone have a wiring diagram for the ac system? The a/c unit won't turn on and i can't charge it until it does. I know i'm missing the wire that goes to the compressor and want to check to see if i have all the other and if they are run right or not. Also any other tips or help would be nice. Thanks in advance guys.
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Old 06-22-2004, 10:43 PM   #2
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The stock green wire comes from the H/VAC panel, into and out the high pressure cut off switch, then goes to both the idle kick up solinoid and the compressor clutch.
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1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles
2006 Ford Focus ZX3 5-speed Stick
2016 Chevy Spark EV
Gone: 2002.5 VW GTI 24v VR6
Gone: 2008 VW R32

Last edited by apstguy; 06-22-2004 at 11:23 PM.
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Old 06-22-2004, 11:34 PM   #3
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anyone have a diagram? so i can check all the other wires and fuses and everything
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Old 06-22-2004, 11:43 PM   #4
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Hope this helps out...







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1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles
2006 Ford Focus ZX3 5-speed Stick
2016 Chevy Spark EV
Gone: 2002.5 VW GTI 24v VR6
Gone: 2008 VW R32
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Old 06-23-2004, 07:30 PM   #5
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yeah that helps a little...shows me what i'm missing
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Old 06-23-2004, 07:33 PM   #6
Chevyguy111786
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what's this....and is it on every unit? does anyone have an a/c wiring harness up for grabs for sale?
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Old 06-23-2004, 07:37 PM   #7
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guess a pic would help
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Old 06-23-2004, 07:38 PM   #8
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ok still didn't work....the connection on the accumulator on the far left...with the wires and white connection.
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Old 06-23-2004, 07:39 PM   #9
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high/low pressure cutoff switch.
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Tyler

1985 C10 305 w/ Bowtie OD TH700R4 3.42 LSD 202,000 miles
2006 Ford Focus ZX3 5-speed Stick
2016 Chevy Spark EV
Gone: 2002.5 VW GTI 24v VR6
Gone: 2008 VW R32
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Old 06-23-2004, 07:42 PM   #10
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Yep, Low Pressure Valve (LPV)
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Old 06-23-2004, 09:40 PM   #11
Chevyguy111786
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alright, i think my LPV is on my high side or liquid line...small line. My accumulator doesn't have a spot for it. now my question is....on the fan switch...the wires leading to it come from behind the ac duct box. and don't have any power to any of them. shouldn't they be coming from the fuse box? somehow at least?
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Old 06-23-2004, 10:01 PM   #12
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ok....i jumped power to the fan blower wires....low, high, and med all run...for some reason the harness doesn't have power. where does the harness connect to get it's power?
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