Painless CJ-5 Rewire

How-To: Rewire a Jeep CJ

Jay KopycinskiPhotographer, Writer

“That light’s still not working,” I yelled to the owner. He spit out a string of obscenities, cursing whatever electrical demons had possessed the Jeep. The electrons were once again dancing like banshees and not at all heading where they needed to go.

Aging Jeeps can start to suffer, with regard to reliability, even when they’re well maintained. Parts age and systems fail despite ardent service and preventative measures. Electrical wiring as a system is subjected to heat/cold cycles, vibration, and exposure to chemicals and the harsh elements of weather. Old wiring insulation can become brittle and crack, while connection points can become resistive or fail due to mechanical breakage or corrosion.

The electrical system on this 43-year-old CJ-5 was suffering from some of those maladies. There were lights that didn’t work and some that did when they shouldn’t have. A previous owner had done some of his own wiring modifications, and that wasn’t helping matters. We decided the best plan for the long term was to rid the Jeep of most of the added wiring and pull the entire factory harness out for replacement.

One can always pursue the hard work of wiring a vehicle from scratch, but we chose to use an aftermarket solution to replace a factory harness and ordered up a Painless Performance direct-fit harness designed specifically for ’76-to-’86 Jeep CJ models. The kit comes complete with an ATC fuse panel; wiring harnesses for engine, interior, and tail sections; and plenty of small parts, extra wire, and electrical terminals. With a chassis ground strap kit and DuraSpark ignition harness kit, there was almost everything to fully rewire the whole Jeep (except for battery cables).

Painless provides a thick reference manual with very detailed instructions on how to rewire the entire vehicle. It includes notes on model variations, how to incorporate aftermarket electrical components, and specifics for wiring a fiberglass tub. Another nice feature of the 148-page instruction book: the full descriptions of each wire regarding its function, size/color, and termination points. This is useful both during installation and later should you ever need to do wiring modification or troubleshooting.

We began by stripping all the existing wiring from the CJ-5 and removing the dash for easier access there. Then, we started installation of the new Painless harnesses using the reference manual as a guide. This process takes time, so it pays to be methodical and understand how the harness is going together.

The interior and tail harnesses are laid out plainly for the most part. The engine compartment harness will require more custom routing and wiring, depending on what you have under the hood. We started from the bulkhead connector and worked our way to the passenger side and forward, wiring items as we encountered them. Keeping the wires bundled and taped with electrical tape every 6 to 8 inches helped keep the wiring organized. When you find you want to reroute or you’ve missed something, cut off the last few tape wraps and rework the harness routing going forward.

We did some function checks to confirm all was working well. Once complete, our entire electrical system looked so much cleaner. Plus, we had confidence that all the electrons would be dancing to our tune and going where they needed to be when we’re out exploring trails in the Jeep.

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