Engine wiring harness - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Tomo** · 03-27-2024, 11:58 AM

My dad just picked up a really clean 85 short bed. The engine harness has been modified several times over the years and I’m thinking it would be best to replace it entirely. The rest of the wiring is in great shape. Any suggestions on a complete under hood only harness?

Prong · 03-27-2024, 04:13 PM

American Autowire or maybe M&H will have what you need.

**1971Stepside** · 03-27-2024, 04:48 PM

Marketplace...find someone parting out a square. Often times the harness is there after the motor and trans are long gone.

**72malibu** · 03-27-2024, 06:08 PM

You've got several options.

AAW, M&H, and Lectric Limited are the ones I'd focus on.

Some part numbers are the same across brands - not sure about the engine harness.

For a total wiring redo, I went with an M&H updated ATO fuse dash harness (a long wait time). I went with Lectric Limited on almost everything else, including the engine harness. Same quality IMO, faster delivery. I chose these because they are exactly like factory (except the ATO fuses) and require no crimping, etc. You'll get what you pay for.

**hatzie** · 03-27-2024, 08:11 PM

Really not a lot to an engine harness on 1986 and prior. I'd just roll my own or fully replace the one or two damaged wires.
Break the engine compartment down into sub-sections.

Forward lighting & horn is separate.
Wiper/washer wiring too.

I call the alternator, and starter separate as well. Look at the 1986 wiring diagrams for the starter and alternator wiring. It varies almost every year.

HEI power, temp sensor, oil pressure sensor, oil pressure switch & choke, and AC compressor.

If you have a feedback carburetor and ESC distributor there are only a few wires between em that run back to the ESC ECM and those are separate from the rest of the engine wiring. The knock sensor wiring is shielded so don't mess with it if it's not damaged.

PowerdbyChevy79 · 04-06-2024, 09:19 AM

M&H is really good.. but I love American Autowire..I have had no issues with their wiring.

Dleslie212 · 04-06-2024, 11:12 AM

I just finished wiring my 77 with a painless kit. The manual alone is worth the money

chris989 · 04-14-2024, 09:15 PM

go to Classic Car wiring and order a laminated sheet.

https://classiccarwiring.com/product...wiring-diagram

even if you replace the entire harness these are worth gold when working on an older car..

I get one for every build in our shop. worth every penny

Chris

03-27-2024, 11:58 AM	#1
Tomo Senior Member Join Date: Apr 2016 Location: Indiana Posts: 213	Engine wiring harness My dad just picked up a really clean 85 short bed. The engine harness has been modified several times over the years and I’m thinking it would be best to replace it entirely. The rest of the wiring is in great shape. Any suggestions on a complete under hood only harness?

03-27-2024, 04:13 PM	#2
Prong Registered User Join Date: May 2007 Location: CO Posts: 475	Re: Engine wiring harness American Autowire or maybe M&H will have what you need.

03-27-2024, 04:48 PM	#3
1971Stepside Almost Satisfied Join Date: Mar 2002 Location: Springfield, MO Posts: 2,932	Re: Engine wiring harness Marketplace...find someone parting out a square. Often times the harness is there after the motor and trans are long gone. __________________ 1971 C10 Stepside. LSx 6.0 with BTR Stage IV, Speed Engineering Headers, 4L80e transmission w/3200 Circle-D Stall. 3.73. Posi. Purchased this truck when I was 17. I started the rebuild (or take apart) in 1993. I have drug it around all over the country in pieces. Finally back on the road in 2021. "I can't complain, but sometimes I still do. Life's been good to me so far."

03-27-2024, 06:08 PM	#4
72malibu Active Member Join Date: Jun 2019 Location: Gaithersburg, MD Posts: 135	Re: Engine wiring harness You've got several options. AAW, M&H, and Lectric Limited are the ones I'd focus on. Some part numbers are the same across brands - not sure about the engine harness. For a total wiring redo, I went with an M&H updated ATO fuse dash harness (a long wait time). I went with Lectric Limited on almost everything else, including the engine harness. Same quality IMO, faster delivery. I chose these because they are exactly like factory (except the ATO fuses) and require no crimping, etc. You'll get what you pay for.

03-27-2024, 08:11 PM	#5
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 4,977	Re: Engine wiring harness Really not a lot to an engine harness on 1986 and prior. I'd just roll my own or fully replace the one or two damaged wires. Break the engine compartment down into sub-sections. Forward lighting & horn is separate. Wiper/washer wiring too. I call the alternator, and starter separate as well. Look at the 1986 wiring diagrams for the starter and alternator wiring. It varies almost every year. HEI power, temp sensor, oil pressure sensor, oil pressure switch & choke, and AC compressor. If you have a feedback carburetor and ESC distributor there are only a few wires between em that run back to the ESC ECM and those are separate from the rest of the engine wiring. The knock sensor wiring is shielded so don't mess with it if it's not damaged. __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful. Last edited by hatzie; 03-27-2024 at 08:20 PM.

04-06-2024, 09:19 AM	#6
PowerdbyChevy79 Registered User Join Date: Apr 2013 Location: Houston,Tx Posts: 790	Re: Engine wiring harness M&H is really good.. but I love American Autowire..I have had no issues with their wiring. __________________ 1966 C10 "Mary" 1972 C10 Cheyenne "Betty" https://67-72chevytrucks.com/vboard/...d.php?t=847364 1979 C10 Silverado "The BIG TEN" https://67-72chevytrucks.com/vboard/...d.php?t=841339 C10 Club Texas -HMIC

04-06-2024, 11:12 AM	#7
Dleslie212 Registered User Join Date: Sep 2019 Location: Scottsdale Arizona Posts: 114	Re: Engine wiring harness I just finished wiring my 77 with a painless kit. The manual alone is worth the money

04-14-2024, 09:15 PM	#8
chris989 Registered User Join Date: Dec 2011 Location: Boise, Idaho Posts: 585	Re: Engine wiring harness go to Classic Car wiring and order a laminated sheet. https://classiccarwiring.com/product...wiring-diagram even if you replace the entire harness these are worth gold when working on an older car.. I get one for every build in our shop. worth every penny Chris



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