Wiring Harness

Does anyone have a source for a wiring harness ‘75cj/304. I’ve seen everything but

 

1975 is a single-year harness, the only year with a fuse panel (new for '75) and the straight column with the "bus wheel." In 1976, Jeep went to a GM steering column, which changes the wiring.

What's wrong with the harness you have now?

 

PO doctored it up a lot and I continue to have intermittent issues. Just last night, headlights on, right turn signal won’t flash. Lights off, it works, plus, splices all over the place

 

Intermittant behavior seems more like bad grounds or oxidized connectors than goofed-up wiring. Suggest you clean and reseat every ground and connector and see if that helps. Make sure you have a good ground between the grille and fenders, fenders and body, frame and body, engine and frame. The lighting has grounds to the body steel that are shown on the wiring diagram. Remove each, clean the connector and replace with a new shakeproof washer, if present.

When the grounds go open, the electricity finds another circuit and gives surprising behavior. This is common with the indicators. You need good grounds.

Grounds and connectors have been discussed a lot on this and other Jeep forums. Look at old posts for some discussion if you need more instruction.

There are many "universal" (hot rod) harnesses available on the aftermarket. None of these will have a fuse panel and match your turn signal switch on the original steering column. I suggest you read the wiring diagram and repair what you have. It's not difficult if you take the wiring one circuit at a time. Print out the wiring diagram from the TSM double-size, tape it together, and trace out each wire with colored pencil as you follow it along. You need the 1975 TSM. Use the diagram from the TSM - no other year will match it. Don't use a diagram from a Haynes or Chiltons manual for this - they are full of errors.

Also, any splices that were put in can be removed. You need patience and a little technique; go one circuit at a time, trace out the wires and put back to the original circuit. Typically these are there to add accessories and such, and you can remove the spliced-in wire and replace with a butt connector. This is how I make butt connections - http://www.earlycj5.com/xf_cj5/index.php?threads/142321/#post-1571304 - there are also butt connectors available that include heat shrink tubing, if you prefer.

 

As i pondered the problem, before seeing your answer, the thought of grounds occurred to me. Nearly 40 years as an electrician, yet, i feel like such a noob with this Jeep. I’m going to check all of the grounds. Now, as far as a harness… I see I can buy generic fuse blocks and do my own wiring, its like a siren call. #14 THHN is readily available and I’m wondering if that would cover most of my needs.

 

That's the stranded house wiring? Maybe I'm wrong, but I believe it has a stiff insulation and only a few strands. Automotive primary wire has finer strands that withstand fatigue from flexing and vibration better. The insulation is typically PVC; I don't know is this is better worse or indifferent from the THHN or what... but it's different.

If you go with a hot rod harness, most of them give you a fuse panel with many different colors of wire, with color coding like you have in the factory harness. You can buy a multicolor harness and fuse panel from China for very cheap, like $20? - last I looked a year ago.

It gets real expensive to buy primary wire in all those colors; that's the main thing the hot rod harness gives you.

There is lots of discussion of the hot rod harnesses in old posts here. They are popular for the earlier Jeeps that only have inline fuses, with no fuse panel. Your fuse panel is one with the bulkhead connector as I recall. If you remove it, I think you'll leave a hole in the firewall. It's possible the replacement harnesses or same-era Chevys has the same firewall penetration as the original Jeep harness. Or you could use a harness for a '76-up Jeep and convert the indicators connection to the Spartan-style switch on your column. The GM column has a long single-row connector that carries all the column connections - very common feature of these hot rod harnesses.

 

Maybe I can add one more opinion - the existing wiring layout has value. It's been tested by automotive engineers and time, and having an accurate diagram is valuable. To me, you're throwing away some of the vehicle's value when you rip out the existing wiring and replace with something different. Unless you are willing to document the new wiring as well as the old was documented, the value in the description of the wiring is lost. Look at the wiring diagram from the TSM - you need the TSM - there are both tabular and schematic listings of all the circuits. There is a lot there. The table even shows you what quadrant of the diagram to find each circuit. It shows you wire gauges and colors, and traces (striped wires). It shows you the sizes and locations of the grounding studs, and the sizes of the studs on the accessories. Very complete. With your background, you should like that.

The wiring was a big improvement with the '75 model year. It's one of the things that makes a 1975 CJ neat and interesting. Groovy.

 

Morning XX,

Fellow electrician here. I have wired quite a few cars over the years. From slightly modifying to building a harness from scratch. As has been mentioned, it may be preferable to go in and redo the splices you have found. I have had to redo many splices inherited from previous butchers.

My old boss had a 55 Chevy built, no expense spared. The builder used a generic harness with extra wire, didn't want to cut anything, so they folded the excess wiring up and shoved it under the dash. When I first looked at it you couldn't tell what was what. To compound the problem, they used crimp connectors for everything. Everything on that car worked erratically. Sometimes things worked, sometimes they didn't. I wound up pulling everything apart, cutting everything to length and soldering on new connectors. After that it performed as beautifully as it looked.

Personally I would go through the Jeep and eliminate every crimp connector, and those fire hazard self stripping t-taps, etc. Seen too many of them cause problems. For ease of future diagnostics, get some proper wire colors so the splice doesn't change the wire color on you halfway to its destination. If you can't match it, replace it end to end.

I wouldn't use THHN, it's way too stiff, and for most things in a CJ5 #14 is overkill. The good news is there just isn't that much wiring in a CJ5. Whether you start from scratch, modify a kit, or fix what you got, take it one wire at a time and make it clean and neat. Good luck.

 

You make good points. My “problem”, if you will, is with literally decades of making up panels, seeing the spaghetti plate of wiring is disturbing. I’m going to suppress my OCD and see about saving what I have, and if not, then, rip, tear, gouge !!!

 

I agree on the THHN, and the wire size is a welcome piece to my ears, not being accustomed to small wire. I’ve decided to be patient

 

Once you get the hacked-in PO wiring gone, there's nothing wrong with bundling the existing wires into plastic wire loom secured with zip ties. I'm thinking you're looking under the dash. All the exposed wiring under the hood should already be in loom, as well as the rear light wiring running along the inside of the body. It won't be as neat as a custom job, but it might help to sooth your nerves.

Note that the engineers that designed this didn't use any extra wire for looks, where it would be hidden. It's an added cost. You could splice in additional wire if you want, to make the routing neater. They also did not use any larger wire than the circuit needed, so there's a lot of 16 ga and 18 ga wire in the harness.