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Old 06-07-2019, 09:34 AM   #1
COOP3726
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A/c wiring 5.3l compressor

This may need to go in another section. I need help wiring the 5.3l a/c compressor. I am in the process of wiring my 1985 C10 a/c and I am confused with the wiring. LS1Swap.com states removing all of the a/c wiring from the pinouts, but so far all of the forums I have read say use wires 43,17&55 of the red C2 for the a/c to work. Can someone clarify this wiring procedure and give a wiring diagram? Thanks.
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Old 06-07-2019, 10:35 AM   #2
layinrocker65
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Re: A/c wiring 5.3l compressor

I don’t know how different 85 is from my 74 but I used all the factory a/c wiring and never tired it into the LS harness. I have vintage Air now and it’s still not tied into the Ls harness.
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Old 06-07-2019, 11:40 AM   #3
COOP3726
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Re: A/c wiring 5.3l compressor

I have electric fans and they work off of the LS harness. So I think I need for them to come on when I turn on the A/C. Not sure how to wire the fans to run when the a/c is on.
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Old 06-08-2019, 08:35 AM   #4
homemade87
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Re: A/c wiring 5.3l compressor

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Originally Posted by COOP3726 View Post
I have electric fans and they work off of the LS harness. So I think I need for them to come on when I turn on the A/C. Not sure how to wire the fans to run when the a/c is on.
The fans work independent . They work off the system pressure to know when to come on if using the trinary switch . If you have them wired like factory you need to do nothing for the fans . On my 85 I just wire the compressor to my 85 factory wire and all has been working great for years .
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Old 06-09-2019, 02:03 AM   #5
layinrocker65
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Re: A/c wiring 5.3l compressor

If you have an electric fan, you need to run a trinary switch as stated above. The LS ecm will provide a ground to the fan relay to turn on the fan when the engine requires it for cooling and the trinary switch will send a ground to the same fan relay for when the a/c requires it. If you google vintage air trinary switches, they have a useful video that explains how to wire it.
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53 GMC 2.5 ton COE
70 Chevy C10 LWB 350/465(soon to be 6.0/4L80e)
74 Chevy C10 SWB 5.3/4L80e
91 GMC Syclone 370/4L80e PT88 AWD
92 GMC Typhoon 6.0/4L80e twin 65s AWD
07 RCLB Sierra Duramax
15 Chevy SS 6.2/TR6060 LSA blower
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Old 06-11-2019, 09:15 AM   #6
COOP3726
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Re: A/c wiring 5.3l compressor

O.K. homemade87. I have the fans wired up with the three relays for the ECM to operate them from a ground. Not with the trinary switch. My truck has a Low pressure switch on the accumulator. Not sure if it has a high pressure switch. You said you have yours like this and you just used the original compressor clutch wire and everything works like it should. Is this correct? I can go back and add the ac wires that the ECM recommends to use, if possible, for the High and Low pressure switches. I would rather not because that will mean taking all of the wire loom back off and reworking the wire harness. Any other info will be greatly used.
Thanks.
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Old 06-11-2019, 12:02 PM   #7
homemade87
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Re: A/c wiring 5.3l compressor

Quote:
Originally Posted by COOP3726 View Post
O.K. homemade87. I have the fans wired up with the three relays for the ECM to operate them from a ground. Not with the trinary switch. My truck has a Low pressure switch on the accumulator. Not sure if it has a high pressure switch. You said you have yours like this and you just used the original compressor clutch wire and everything works like it should. Is this correct? I can go back and add the ac wires that the ECM recommends to use, if possible, for the High and Low pressure switches. I would rather not because that will mean taking all of the wire loom back off and reworking the wire harness. Any other info will be greatly used.
Thanks.
If you do not have the high pressure trinary wires going to the ecm the fans will not work with the ecm at all . The ground trigger wires you have going to the relays from the ecm will not do anything . The trinary tells the ecm what to do for the fan trigger . All you will need to add is the high pressure trinary . I used the original truck low pressure switch and the original compressor clutch wire .
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Old 06-13-2019, 12:04 PM   #8
COOP3726
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Re: A/c wiring 5.3l compressor

Can you send me a wiring diagram of how you did yours?
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