Good evening all,
I am helping my dad out by getting his jeep up and running again. This Jeep YJ being 26 years old, he wants some replacement parts. One of those are a new wiring harness. This jeep is a 4.0 straight six manual.
O'reillys is attempting to find one for me with no answer yet.
I cannot find any brand new harnesses online, that will come pre-made. Perhaps I'll have to reassemble a new one?
I am wondering which direction to look, if there is some hidden gem for premade wire harnesses that I don't know about. Or is it even worth it?
Any help is greatly appreciated!
There are no new ones. Buy from eBay or fix up the old one. Are there specific issues with the existing wiring that warrant a replacement?
The YJ is broken up into multiple harnesses that connect together:
Headlight Harness: includes horn, washer motors, and all front lighting - headlights, parking lamps, fog lights (if equipped), side markers). This one starts at the bulkhead fuse box connection on the firewall and runs down the driver fender and then over through the grille. The headlight harness will usually only include wiring for fog lights if the YJ was equipped. Same goes for the dash harness with the fog light switch connector, it is usually missing the connector if the vehicle had no fogs ever. Sometimes this is not the case, and a Jeep without fog lights may still have all the wiring. It is a messy mix. Mine had no fogs and no wiring or switch connector for them.
Engine harness: Goes to injectors, sensors, sending units, etc. Starts at the PCM, goes up to the firewall and to the engine, down the engine and back around, then down the passenger side of the engine at the firewall and out to the transmission, transfer case, and fuel tank. It connects to the body harness at 2 connection points, 2 cube connectors, one located at the relay box by the alternator and another one at the firewall. These connections are how the PCM gets power and how the sending unit data gets back to the gauges.
Under hood Body Harness: This one includes the relay box, and is really how power gets from the battery to all the vehicle components. The relay box has a bunch of wiring coming out of it, some goes to the engine harness through the connectors previously mentioned, but most of it goes up to the top of the firewall and over to the bulkhead connector (the same one the headlight harness goes into. The headlight harness actually clips into the bulkhead connector on the under hood body harness.
Often eBay will sell the engine harness & under hood body harness together and just call it "engine harness".
Under dash body harness: This one feeds all dash components (speakers, gauges, radio, heater, courtesy lamps, etc). It runs from the fuse box and carries power across the dash. It has two boxy connectors (gray and black) by the fuse box that connect to the rear body harness.
Rear body harness: This one feeds tail lights, seat belt buckle sense, and the appropriate lack of wiring for a soft top, or wiring/hose for a hard top, hard top defroster (if equipped), hardtop window sprayer, and the hardtop dome light. There were multiple harnesses for all these options, they built the harness depending on what features you have. Meaning my harness has everything but hardtop defroster wiring since my hardtop didn't have a defroster.
Hope all that helps. Nobody makes a full YJ harness. Painless makes a harness for the body of an 87-90 carbureted YJ. It is not painless, as there are a lot of items that have to be kept and reused if still running one of those engines. For a fuel injected YJ 91+, you can still find all 5 of the harness types on eBay, in their different variations as well. Just search. They're all old so unless you're having problems, I'd keep what is there.
