Wiring harness questions?!

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JohnnySwell
Posts: 35
Joined: Wed May 20, 2020 3:36 pm

Wiring harness questions?!

Post by JohnnySwell »

Hey all! I've lurked on here before but I'm a new member and looking for some advice on my recently acquired 78 Chief.

I know these old FSJs are know for faulty and terrible wiring and my battery just continues to draw power, my rear power window works when I jiggle the wiring around, and my fuel gauge always stays on E. I think I've found the issue with my battery draining, found a light under the dash (not door ajar light) that constantly stays on and think it's an open circuit and tried following the wires but seems like I have to take apart the dash.

I think my first priority is to fix the headache of wiring and I'm leaning towards wanting to completely swap out for a Z&M or a Rebel Wiring kit. My dash pad is kinda beat-up too so I'm looking for a new one at the moment and my windshield looks like it needs to be replaced too. I'm mentioning this because I've heard how tough it is to remove the dash pad and most just remove the windshield to do so.

I'm looking for some advice on wiring kits. I'd like to get something that works with my rear window as well. I know an older gentleman that used to frequent this and the other FSJ forum unfortunately passed away but used to make wiring harnesses for the rear window. Has anyone seen something mocked up since then? What are things to remember or pointers while attacking the wiring swap? Also looking to see where I could get a decent dash pad and a new windshield?


I'm excited to finally start fixing up my dream Jeep so any and all pointers are much appreciated! Thanks!


-Johnny
Johnny B

1978 Cherokee Chief

I'd love some input on my build here:
https://www.fsjnetwork.com/forum/viewto ... 12&t=20266
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tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Wiring harness questions?!

Post by tgreese »

First, I'm not convinced the wiring in these Jeeps is any worse than other cars from the era. A 1978 Jeep is now 43 years old - way beyond the concern or intention of its designers and builders.

Second, I feel that the major motivation of owners that feel they must remove all the factory wiring and replace it with a pre-made hot rod harness comes from frustration, not any kind of real analysis. Wiring in automobiles in this era is trivially simple, compared to either modern cars or other areas of process control you might consider. It's all DC. and it uses one big ground plane (the body and chassis) for ground return. Not difficult.

Working under the dash is not fun, but realize that the factory put the wiring in these cars on an assembly line. It all unplugs into easily handled harness units. Remove the instrument cluster - it's actually quite easy in these Jeeps. You can repair what you need to, even if it looks daunting and terrible now. Not rocket science.

This is your opportunity to learn some basic skills and gain some basic electrical knowledge. Not just theory, but practical knowledge. Commit to it and make the effort, and you will be rewarded.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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Blueman85
Posts: 31
Joined: Fri Jul 24, 2020 10:57 am
Location: Osprey, Florida

Re: Wiring harness questions?!

Post by Blueman85 »

Let me first say that I am also brand new to these Jeeps and from my very limited experience, I would recommend Tims advice above. Try not to rush to get the new this or that or "overthink" simple procedures like I did. Trust me, its time consuming and not fun trying to make heads or tails of wiring under the hood and dash, but in the end you will continue to gain confidence like I am.

BTW: Removing the instrument cluster is easy, at least on an '85. My 14 year old did ours. Just be sure to disconnect the battery. From what I've read, thats where all hell breaks loose.
1985 GW- 287k, 360/T727/229, AMC 20, Edelbrock AVS 1906, Edelbrock Performer manifold, Hedman hedders

weeegoneeer
Posts: 230
Joined: Wed Apr 26, 2017 10:34 am

Re: Wiring harness questions?!

Post by weeegoneeer »

Let me preface: Any time you dig into wiring on these old rigs, you may find DSPO modifications that more or less work but are confounding. If they work, you want them to continue working so keep a record of how they work.

Z&M makes a REALLY decent harness - especially the engine harness. They have the actual connectors where possible, and where impossible ship it with weather/metripaks. It is spendy though. Also - if you get the dash harness - really verify all of the connectors are correct and the fusebox is arranged the same way before starting. I didn't do this and had to modify to work. It probably isn't their fault - I think someone mixed components on my truck.

For my dash harness, I actually just removed it / bagged & tagged / photos of every connector in place in the car — EVERYTHING. Bought a bunch of wire in the common gauges (TSM is awesome to know gauging of the wire). Couldn't find a source for wires with traces so hit them with a paintpen. Also, you can still buy all of the terminals used in the connectors so you have a straight soldered connection, not a splice.

Take the old harness, unravel it (be prepared for your hands to be covered in gooey old duct tape adhesive!), grab a huge piece of cardboard and pin the wires, paying attention to pin where the original harness was bunched / branched. Recreate the original layout with the new wire. Pay attention to the junctions. Release the old terminals from the connector using terminal remover tools. Do things one step at a time.

There were more than a few "what have I done?!?! I've ruined my Jeep!" occasions. Patience, service manual from oljeeps, and circuit tracing brought me back. Was also able to undo some sketchy alterations the PO added with solderless crimp splices, make a "factory fit" for a pile of additional electronics I've added. Was worth it and now know exactly how my truck is wired, drew a schematic of it so I don't accuse myself of being a DSPO (DSCO?) in the future. Took about five weeks of after work effort though.

FWIW - you don't need to remove the dashpad to do the harness - just the cluster. If you are pre '87, have a write up here for removing the cluster: http://www.forums.ifsja.org/showthread.php?t=182503

Would I do it again? Hell no. I'd trace back and correct / add what needed to be corrected added instead of going thermonuclear.

Too long didn't read: Document what is there in photos, bags and tags. Z&M over race harness. Don't do work you don't need to.
1984 GW

Topic author
JohnnySwell
Posts: 35
Joined: Wed May 20, 2020 3:36 pm

Re: Wiring harness questions?!

Post by JohnnySwell »

Hey guys! Just figured I'd give you an update.

First off, thanks for all the recommendations and tips. I greatly appreciate it!

I started on my Chief about 2 weeks ago on my days off from work. I decided to go all out and just rip out the dash and interior so I am slowly and steadily labelling and taking pictures of everything wired under the dash. I'm basically studying the entire wiring diagram lol. I plan on grabbing a new wiring harness off of Z&M Jeeps as the replacement.

Also, I'm thinking about going digital with a modern/resto-mod dash gauge. Something like Dakota Digital? Not sure yet but I'll have to look more into that. I'm planning on updating the sound system with a DIN style head unit and adding and amp somewhere to really make it sound nice so I'd love some recommendations on where to put the amp and sub? I'm thinking sub under driver seat??

My dash pad is cracked so I'm thinking about taking that to an upholstery shop to clean her up and cover the top vent. I also plan on sanding down the metal part of the dash and refinishing that (maybe in a raptor-liner finish)



I might start a build thread of some sort or maybe a vlog of my build and post it on here/youtube just to document my journey of my dream Jeep so I'll let you guys know if I decide to do that!



-Johnny B
Johnny B

1978 Cherokee Chief

I'd love some input on my build here:
https://www.fsjnetwork.com/forum/viewto ... 12&t=20266

SkylinePCG
Posts: 72
Joined: Tue Apr 16, 2013 11:28 am

Re: Wiring harness questions?!

Post by SkylinePCG »

Z&M makes great stuff. I got his engine bay harness and it was perfect. Length, fasteners, loomed, terminated. It was spot on.

You will want to use your old harness as a reference for routing, even if it’s not in the exact same place(s) it started.

oscarj777
Posts: 5
Joined: Fri Apr 30, 2021 10:04 pm

Re: Wiring harness questions?!

Post by oscarj777 »

Looking to replace my harness on 88 Grand Wagoneer. Any suggestions?

oscarj777
Posts: 5
Joined: Fri Apr 30, 2021 10:04 pm

Re: Wiring harness questions?!

Post by oscarj777 »

Looking to replace my harness on 88 Grand Wagoneer. Any suggestions?
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tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Wiring harness questions?!

Post by tgreese »

oscarj777 wrote: Sat May 01, 2021 12:05 am Looking to replace my harness on 88 Grand Wagoneer. Any suggestions?
Just fix it. Unless you had a fire, straighten out what the PO has done and run it.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

oscarj777
Posts: 5
Joined: Fri Apr 30, 2021 10:04 pm

Re: Wiring harness questions?!

Post by oscarj777 »

My initial thought too. Thanks for bringing me back from a rabbit hole! I am restoring this having having it for 20 years. Just found this forum and already seeing so many great ideas/advise.
Thanks again.
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FLeetFox
Posts: 243
Joined: Tue Apr 17, 2018 7:05 am
Location: Blue Ridge Mtns

Re: Wiring harness questions?!

Post by FLeetFox »

Tim's right. Buy a good Fluke meter. Blow up the wire diagrams and spend a couple of bux at Kinkos and have them print them huge on a plotter. Then buy a box of different color high lighters It's a 15 circuit harness, Most of us can do this, it's not sequencing a genome. Sorry, venting a little, the point is simply that if your having a problem with one wire or a few, that you can't find, replacing it all with new spaghetti you don't understand just invites more problems. Not trying to be harsh, but try getting in there and thinking through it before throwing the baby out with the bath water.

Fleet Fox
I do things my way, and I pay a high price.... JCM

oscarj777
Posts: 5
Joined: Fri Apr 30, 2021 10:04 pm

Re: Wiring harness questions?!

Post by oscarj777 »

Thanks for the input.

Srdayflyer
Posts: 398
Joined: Mon Mar 18, 2019 2:08 pm

Re: Wiring harness questions?!

Post by Srdayflyer »

i am restoring an 83 cherokee, and unless you had and engine fire ckean up the harnass, my wire loom covering was brittle and just worthless, i bought new wire loom covering of different sizes and started with that , it cleaned up nicely invest in a good factory jeep manual, and not a cheap chiltons type , ive just about worn mine out , invest in zip ty's or tywraps to clean up loose wires, and pick a point and start to tidy up the wiring especally in the engine bay, im nearing the paint stage on my project if installed a 4 " spring lift, redone the fuel system at the gas tank parking brake cables, brakes, inspected heater core , a/c evaporator core, replaced a/c hoses ,repaired the dash cover {no small feat} list goes on and on
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tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Wiring harness questions?!

Post by tgreese »

oscarj777 wrote: Sat May 01, 2021 7:07 am My initial thought too. Thanks for bringing me back from a rabbit hole! I am restoring this having having it for 20 years. Just found this forum and already seeing so many great ideas/advise.
Thanks again.
Sorry if my reply seemed short. Sounds like you have things well in hand. Post up if you have questions about specific issues. :-bd
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.
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