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

ullose272 · Yesterday, 12:18 PM

I have a '68 GMC that over the years has had different updates and mods done, MSD ignition, Electric fans, one wire alternator. it has some electrical gremlins and extra original wires that i would like to clean up. i have a full wiring schematic, but i wasnt sure which wires could just just go away.

anyone have thoughts?

**PbFut** · Yesterday, 01:01 PM

I just finished the electrical last month. I found the fire had destroyed most of the engine harness and some of the headlight or main harness. With HEI the engine harness is easy and only has 3 wires really needed. Purple to starter solinode, green to water temp, and I think yellow to coil. The original yellow circuit has a splice to aux pin on solinode not needed with HEI, but the lead from fire wall connector needs to be replaced if original because it's a stainless steel resistor wire. That gives you a bunch of spare ports in the engine harness firewall connector to add extra circuits. The headlight harness is pretty much full at the connector and not much to eliminate. You can drop one of the leads for battery gauge if you are using the other for volt meter replacement. If you are using battery meter, and heavy loads like fans, this is a must to add a jump from main splice to a added junction block on left side fender. Then hook all non factory loads to that added junction block. This will keep your battery gauge functioning correctly. Be sure to fuse link thatadded main splice jump. That's about it.

**PbFut** · Yesterday, 01:10 PM

Forgot the brake warning wire. It is in the engine harness side of the connector. The photo shows ecu and added fuse box. 3 wires had to be added to the factory aux hole as all the pins were used up. I have 3 added meters, 3 added indicator lights aux battery relay trigger 3 fan triggers, fuel pump and ecu.

Willshook · Yesterday, 01:34 PM

I did the same thing both ways on my '72; there was a bunch of old stuff and wiring associated, and new stuff I added with kinda lousy, quickly-done wiring.

I bought one of those nice full-color laminated wiring diagrams, and just started labeling stuff. Then I slowly worked through and removed unused wiring, and re-did everything I had done before with good crimps, shrink wrap and nice routing. Zip ties to clean up.

Slow and steady with a good DVOM, working through the wiring diagram.

LS short box · Yesterday, 04:32 PM

My .02.
I think I would replace the complete wiring harness. I've had really good luck with Painless universal 21 circuit on a few hot rods. AAW also get good reviews.
I also like to hide wires on my LS swaps. With a new wiring harness its easy to hide wires.
Pic.

Willshook · Yesterday, 06:51 PM

Quote:

Originally Posted by LS short box

My .02.
I think I would replace the complete wiring harness. I've had really good luck with Painless universal 21 circuit on few hot rods. AAW also get good reviews.
I also like to hide wires on my LS swaps. With a new wiring harness its easy to hide wires.
Pic.

That is absolutely stunning work!

Do you have a build thread somewhere?

54blackhornet · Yesterday, 06:52 PM

Key word here is One Wire.

brandnew72 · Yesterday, 07:21 PM

I removed probably a mile of wiring out of my 72. Traced 1 and removed the extra. One at a time. It's still what I'd call messy from the PO but better. I don't like that they put the fuse box in the cab. Id rather it be in the engine bay by the original location. But it'll take some more rework to do that.

But when I do, one wire at a time lol.

Bodied67 · Yesterday, 09:30 PM

Quote:

Originally Posted by LS short box

My .02.
I think I would replace the complete wiring harness. I've had really good luck with Painless universal 21 circuit on a few hot rods. AAW also get good reviews.
I also like to hide wires on my LS swaps. With a new wiring harness its easy to hide wires.
Pic.

This looks killer!

LS short box · Yesterday, 09:31 PM

I did a build thread on here but don't remember the name. LOL. It was a 68 C10. It was a great project. I started out with a real clean truck to begin with.
Couple things.
I moved the fuse block back from the fire wall and filled the hole. Then made a smaller hole behind the left inner fender just for the chassis wire harness. Really not that many wires that go forward and back. I ran them along the left frame rail to the rad support. Same with the rear chassis wiring along the left frame rail.
All the LS/ECM wires out behind the engine by the right cylinder head into the cab to the ECM and fuse/relay block. Fuel pump wire cross over behind the engine and then down the left frame rail with the chassis wiring harness.
My current project is a LS3 into a 80 Camaro. I ran all the front chassis wiring harness wires as they did as stock over the left fender well.
Thanks for the kind words on the 68.

Yesterday, 12:18 PM	#1
ullose272 Registered User Join Date: May 2011 Location: Boise, ID Posts: 32	wiring cleanup I have a '68 GMC that over the years has had different updates and mods done, MSD ignition, Electric fans, one wire alternator. it has some electrical gremlins and extra original wires that i would like to clean up. i have a full wiring schematic, but i wasnt sure which wires could just just go away. anyone have thoughts?

Yesterday, 01:01 PM	#2
PbFut Senior Member Join Date: Feb 2022 Location: Ca Posts: 712	Re: wiring cleanup I just finished the electrical last month. I found the fire had destroyed most of the engine harness and some of the headlight or main harness. With HEI the engine harness is easy and only has 3 wires really needed. Purple to starter solinode, green to water temp, and I think yellow to coil. The original yellow circuit has a splice to aux pin on solinode not needed with HEI, but the lead from fire wall connector needs to be replaced if original because it's a stainless steel resistor wire. That gives you a bunch of spare ports in the engine harness firewall connector to add extra circuits. The headlight harness is pretty much full at the connector and not much to eliminate. You can drop one of the leads for battery gauge if you are using the other for volt meter replacement. If you are using battery meter, and heavy loads like fans, this is a must to add a jump from main splice to a added junction block on left side fender. Then hook all non factory loads to that added junction block. This will keep your battery gauge functioning correctly. Be sure to fuse link thatadded main splice jump. That's about it.

Yesterday, 01:10 PM	#3
PbFut Senior Member Join Date: Feb 2022 Location: Ca Posts: 712	Re: wiring cleanup Forgot the brake warning wire. It is in the engine harness side of the connector. The photo shows ecu and added fuse box. 3 wires had to be added to the factory aux hole as all the pins were used up. I have 3 added meters, 3 added indicator lights aux battery relay trigger 3 fan triggers, fuel pump and ecu. Attached Images

Yesterday, 01:34 PM	#4
Willshook Registered User Join Date: Jun 2019 Location: Chehalis, WA Posts: 151	Re: wiring cleanup I did the same thing both ways on my '72; there was a bunch of old stuff and wiring associated, and new stuff I added with kinda lousy, quickly-done wiring. I bought one of those nice full-color laminated wiring diagrams, and just started labeling stuff. Then I slowly worked through and removed unused wiring, and re-did everything I had done before with good crimps, shrink wrap and nice routing. Zip ties to clean up. Slow and steady with a good DVOM, working through the wiring diagram.

Yesterday, 04:32 PM	#5
LS short box Registered User Join Date: Jun 2015 Location: Carlos MN Posts: 2,208	Re: wiring cleanup My .02. I think I would replace the complete wiring harness. I've had really good luck with Painless universal 21 circuit on a few hot rods. AAW also get good reviews. I also like to hide wires on my LS swaps. With a new wiring harness its easy to hide wires. Pic. Attached Images Last edited by LS short box; Yesterday at 08:42 PM.

Yesterday, 06:52 PM	#7
54blackhornet Registered User Join Date: Jul 2008 Location: Eastern Oregon Posts: 2,416	Re: wiring cleanup Key word here is One Wire. __________________ 71 C-20 07 Magnum RT AWD

Yesterday, 07:21 PM	#8
brandnew72 Registered User Join Date: Nov 2024 Location: Charleston, SC Posts: 23	Re: wiring cleanup I removed probably a mile of wiring out of my 72. Traced 1 and removed the extra. One at a time. It's still what I'd call messy from the PO but better. I don't like that they put the fuse box in the cab. Id rather it be in the engine bay by the original location. But it'll take some more rework to do that. But when I do, one wire at a time lol.

Yesterday, 09:31 PM	#10
LS short box Registered User Join Date: Jun 2015 Location: Carlos MN Posts: 2,208	Re: wiring cleanup I did a build thread on here but don't remember the name. LOL. It was a 68 C10. It was a great project. I started out with a real clean truck to begin with. Couple things. I moved the fuse block back from the fire wall and filled the hole. Then made a smaller hole behind the left inner fender just for the chassis wire harness. Really not that many wires that go forward and back. I ran them along the left frame rail to the rad support. Same with the rear chassis wiring along the left frame rail. All the LS/ECM wires out behind the engine by the right cylinder head into the cab to the ECM and fuse/relay block. Fuel pump wire cross over behind the engine and then down the left frame rail with the chassis wiring harness. My current project is a LS3 into a 80 Camaro. I ran all the front chassis wiring harness wires as they did as stock over the left fender well. Thanks for the kind words on the 68. Attached Images



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.