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Discussion Starter #1
The wiring in my Jeep is a rat's nest of cobbled together crap from multiple previous owners. I currently have bouncing gauge needles, dash lights coming on when I step on the brake, a few non-working (new bulbs) marker lights and, if I don't turn off the main power switch (big one on the floor), the battery will drain overnight.

So I'm planning on tackling the wiring as the next item on my to-do list.

My question is this: Does anyone make a new, reproduction or even remanufactured wiring harnesses for early YJs? I figured it might be a bit more expensive than just going at it with a multi-meter, but it would save me a bunch of time and headaches.

I've got an '88 with the 2.5L TBI engine. IIRC, that engine was only available from '86-'90, so even finding a junkyard pull is proving difficult.
 

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Electrical problems can be a PITA to deal with and take patience and perseverance and good troubleshooting skills. Painless Wiring makes factory replacement chassis harnesses for the 1987-1991 YJ, including factory style bulkhead connector and fuse block. The harness does not include any wiring for fuel injection or computer.

Gonna be a wee bit more expensive than your typical multimeter though - the harness costs about $900. I honestly think you might want to give troubleshooting a shot before dropping nearly a grand on a replacement wiring harness. If the harness was burned out by a fire or otherwise destroyed it would be a different story.

FWIW, the dash lamps are connected to the park/tail circuit which lights up the rear tail lights, side markers and turn signal markers when you turn on the parking lamps/headlights. The brake lights are powered by a different circuit, but use the same bulb. You likely have a short crossing over from the haz/stop circuit and feeding back into the park/tail circuit causing the dash lamps to light up (probably the turn signal and side lamp markers too) when you step on the brakes.
 

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The most common electrical problems can usually be traced to bad grounds. Being that jeeps are usually very rusted (yes even the ones that look like they are not!!!) a bad ground or grounds are a very real possibility. Get the factory service manual (not chilton or haynes!!!!!) and find the ground points for the circuits that are giving you trouble. It takes a lot of time and patience, and is a ROYAL pain in the azz, but it will be much easier and cheaper than replacing the entire harness. It may not be the grounds, but it is a good place to start.

Or you can leave the keys in the ignition, tape the title to the windshield, walk away and go buy a Honda Civic. To me, this is the best option!
 

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Discussion Starter #4
So I started to tackle the problem with my multimeter when, in some random Google searches for wiring diagrams and/or pictures, I came across a forum post from someone having the exact same issue as me. Instead of the usual "Good luck tracking that down" type of replies, someone in that thread suggested checking the tail light bulbs.

It seems that a burned out filament in one of the dual filament bulbs can cause an open circuit situation. Since all of the lights (parking, side markers, turn signals, dash lights, etc.) are on the same circuit, there can be some weirdness like I was experiencing. So I stopped on my way home from work yesterday and bought a bunch of new bulbs. I mean, for less than $20 worth of light bulbs, it was worth a shot.

I am pleased to report that after swapping in the new bulbs, all of my strange light issues went away! All my parking/running/signal/brake/dash lights are back to functioning like they should!

After all the reading I've been doing about Jeep wiring (especially grounds) I still plan on going through some things but, at least for now, everything is working again!
 
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