Tail light / Brake light / Rear turn signal fuse

I've had my 1972 CJ-5 for about 10 years. Previous owner had done a lot of work on it, but the electrical system was pretty messy. All the critical electrical parts were working (lights, signals, etc), but there are a lot of things that still aren't functioning. In short, I haven't had the time or inclination to get a new harness and redo it all, but I'm still hoping to some day. That said, it's very difficult to trace any of the wires or determine what the glass fuses match up with. Really, it's hard to tell what's original and what's been added.

The other day my tail lights quit working. Brake lights and rear signals are out too (front signals, running lights, and headlights all work fine). I believe the rear lights are all on the same circuit, and that my problem is simply that a fuse is blown or just dirty. But like I said, my wiring is a mess. Can anyone tell me what fuse to check? The fuse "block" on the driver's side firewall near the headlight switch appears to be original, but it's hard to tell. I don't have another to compare it to, so hopefully someone out there can lend a hand. Thanks!!!

 

72 shouldn't have a fuse block just glass fuses. Front turn signals working? Check the harness at the rear and make shure it's not pinched.

 

It has glass fuses. There is an array of them near the headlight switch. Not technically a fuse block, but several mounted in a holder. Is that not standard? Like I said, hard to tell what's original and what's aftermarket.

Yes, front signals work.

 

'72 only has inline fuses, no fuse block. The first year for a central fuse block in a CJ-5 is 1975. The FSM for '72 is a little different in that it has an actual line drawing of the wiring harness, with the connectors and wires drawn in. All the other years of FSM that I've seen have the traditional circuit diagram. You can look at the 1974 wiring diagram here http://oljeep.com/gw/74_tsm/22-7-CJWiringDiagram.pdf - this will be very close to what a '72 has.

If you don't have the FSM for your year I'd suggest you get it. RockAuto has your manual in PDF form for about $20, and bound form for ca $35. 1972 JEEP CJ5 5.0L 304cid V8 Repair Manual | RockAuto Don't buy the Haynes or CHiltons manuals. They try to cover too many years and are full of errors.

The only way to deal with wiring is to get your meter or test light and trace out every circuit. What I used to do is go to my local library and photocopy the diagram from the closest year manual they had, and blow it up on several sheets to double size. Then I'd take my colored pencils and trace over the wires in the wire color as I tested them. The electrical principles of car wiring are very simple - just refuse to be overwhelmed by the number of wires and take one circuit at a time, from one end to the other. Keep at it until you have found the fault.

 

Thanks Tim! Great tips.

I had a Chilton's but can't find it. Glad to know I shouldn't stress over its loss. I think I will get the FSM like you advise.

Now if I can just find a cure for color-blindness, I'll be able to get things sorted out in a snap. Otherwise, I'll just resort back to asking my wife to come out and tell me what color each wire is... which she loves doing

 

FYI you can pick up good used manuals on eBay. I recently got tired of my digital copy images being blotted and I bought one off eBay. Was around $40 and I already paid for it with the diagram I needed.

 

One thing it may be that's a quick and simple fix, Jeep grounded the tail light assembly to the inner fender. Not only does steel not conduct electricity well as copper does and the inherent corrosion at contact areas it may just be as simple as finding the tail light ground and taking a wire brush attachment to your drill, grind away all of the oxidation from the ring terminal and the mounting surface, then during reassembly coat all surfaces with dielectric grease which will inhibit oxidation further.

 

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Hopefully, you've already figured this out and I'm late to the party, but in the event you haven't, there are wires that run from the turn signal switch on the steering column. They run on the outside of the steering column and then run into a plug just under the dash with about six terminals inside. That plug used to give me fits and would cause similar problems to what you're experiencing until I just rewired my whole Jeep. If you've had that many accessories go out at once, that plug would be the next thing I'd check after the fuses. I believe that all the accessories which quit working for you have connections with that plug. After years of dealing with the same issues of hard to locate inline fuses, weak headlights, decayed and piecemeal wiring, I decided it was easier, safer, and more reliable to modernize everything. I just bought auto parts store fuse blocks, relays, and wiring and did everything from scratch. Luckily, Jeeps are fairly simple and it's not particularly expensive. [/URL][/IMG]Good luck.

 

Conor78, Did you ever get this fixed? What was the issue? I have a 1972 CJ5 and I have the exact same symptons going on right now that you do. Again from P/O making this a wiring nightmare, I don't trust my Jeep, but the basics are still intact. I'm really struggling just to find fuses and feel like a contortionist trying to get under the dash. I'm probably going to have to take the seats out next to get up under there if I can't find the fix for this soon.

 

Do you have the TSM for 1972? It will really help you.



This is from section 3 of the '72 TSM. Section 22 has drawings of the wiring with all the wires and colors labeled - not a real schematic diagram, but perhaps more helpful if you aren't familiar with reading schematics. The '73 or '74 manual has a schematic that is pretty close and may help you. You can find a '74 TSM online here: Jeep® 1974 TSM online

PSA - Which Manual Should I Buy?

Likely you should start a new thread with a new question, rather than hijacking an existing thread. You'll get more and better responses.

 

Thanks Timgr. Unfortunately I don't have the Technical Service Manual. I do have a Chilton (useless in my opinion, I think I could have wrote that book its so bad) and the other one I have is the Jeep CJ Rebuilder's Manual by Moses Ludel which is excellent for everything mechanical. He includes schematics to some degree in there, but unfortunately my jeep doesn't have much left in common with the original schematics nor your TSM above, however I do appreciate you posting this for me and I will try to make some use out of it. I think one of the biggest reasons I'm having trouble is because those directional flashers are sitting above my steering column and column frame which is why I'm having so much trouble tracking it down. I found two newer style GM 552 flashers that aren't even on my schematics and I can't find any inline glass fuses to speak of. They could be under some electrical tape, but I'm sure hunting around for them. I would have thought I would have found them. I'm so close to ripping out all of this wiring and starting over.

One other question. The switch/lever on the column (Sparton). If that goes bad, I understand you need to rebuild them. Dumb question: If they go bad would it cause a short if there isn't a connection, making my brake lights and turn signals not work? Again regular lighting is fine. Just brakes and turn signals won't come on and I don't have any flasher lights coming on in the dash, nor am I hearing any clicking from the flashers. I actually don't think the flashers are bad because if they were most likely the light would stay on solid if I completed the circuit. I think I lost the circuit somehow. Especially because I have two symptoms at the same time. Any other advice I'm all ears... before I take it to one of my local shops. I'm confident mechanical stuff, but electrical stuff drives my head wirey...

 

the brake lights run through the turn switch the connector on the switch is a good starting point.

 

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$22.99 from RockAuto. Get on it.

Working under the dash is a pain, no doubt. I'd take the seats out and lay on the floor, looking up, if I had a lot to do. Trace it through one wire at a time. Check your grounds. The wiring of one of these Jeeps is not complicated, if you consider one circuit at a time. Refuse to be overwhelmed - it's only complicated if you try to understand it all at once.

There is also text in the TSM that tells you about the circuits.