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Fri Sep 01, 2017 10:14 am

I just got pulled over by a cop (on Base, no less), and while he was telling me to slow down a bit, he asked to see my brake lights. It turns out I have no brake or backup lights!

Before I start tearing the car apart looking for the bad wires, is there a point that's common for failure to the rear end?

The tail lights and turn signals both work. Fuse#2 appears to be good.

Thoughts?

Fri Sep 01, 2017 10:26 am

I do have the wiring diagram, and am tracing lines....

Fri Sep 01, 2017 7:39 pm

Is the wiring original? Did you do anything recently that may have "disturbed" the wiring?

Fri Sep 01, 2017 10:10 pm

Always check the ground wires, poorly grounded lights may work, but your brake and back up lights are usually higher wattage bulbs and need a really good ground.

Sat Sep 02, 2017 7:47 am

I did wash the poor car, but that's all. I replaced the fuse and checked the grounds in the engine compartment on each side. The wiring doesn't look to me like it's original (lots of electrical tape wrapped around the wiring).

I want to check start checking at the fuse box with a meter. The fuse box really seems to be the only place where all four lights are common. I don't see both the brake switch and the backup switch failing at the same time.

Sat Sep 02, 2017 12:41 pm

We can use a little deduction to help us out. Let's start with the backup lights. Follow along on the wiring diagram, and we'll trace current from the battery to the grounds at the lights., and make some deductions.

Battery to starter.
Terminal 50 on the starter to terminal 50 on the key switch via a red/black wire.
Leaves the key switch as switched power, goes via a black wire from terminal 15 on the key switch to the upstream side of fuse 1.
Travels over to the upstream side of fuse 2 via a bus bar, and leaves fuse 2, unfused, where it goes off via a black wire to the engine compartment and terminal 15 on the coil.

Here's the deductive part. The engine runs, so we know power is making it to the coil, and that all the wiring described above is functioning. So for the back-up lights, your problem lies at the back of the car.

Leaving terminal 15 on the coil, power goes through an inline fuse to the back-up switch, and then after the switch it goes through a splitter, off to the bulbs, and finally to ground.

Have you checked the fuse in the fuse holder? Have you looked at the bulbs? i know that sounds a little like the IT guy who says to you over the phone "Is your computer plugged in? Is it switched on?" Sorry. Many times I have woven a fantasy in my mind about why something is wrong with my car, and that fantasy has prevented me from checking the obvious.

As for the brake lights, we will be less helped by deduction. But let's run through the process.

Battery to starter.
Starter to key switch via red/black wire.
Switched power to fuse 1 via black wire, jumpered via bus bar over to upstream side of fuse 2.
Through fuse 2, and then off to the brake lamp switches via a black wire.

The horn is also powered from the downstream side of fuse 2. Does the horn work? If yes, then the wiring is all good up until that point.

From the brake lamp switches the power continues away via a black/red wire to the engine compartment, to a 4-way connector beneath the right tail light assembly. From there it is distributed to the lamps, and finally to ground.

Do you have one of those voltmeter probes that pierces the insulation of the wire to allow a reading to be taken without having to disconnect anything or remove insulation? Very helpful.

So I would check to see if power is making it back to that 4-way connector in the engine compartment via the black/red wire. Key switch on, with a helper pressing the brake pedal. From there it's good old fashioned leg work.

Good luck.

Edited to add: If the key switch is left on for a more than a minute or so and the engine is not running it is possible to cook your coil.

Sat Sep 02, 2017 5:35 pm

Thanks Captain! Your post is most helpful. Unfortunately, my (aftermarket) horn is no longer on the same circuit (I think it's on fuse 10 now, but I may be wrong about that). I also don't think I have those connector blocks below my rear lights. My suspicion is that the car has been totally rewired at some point in the past, and those blocks were eliminated.

What I do have, on the passenger side, is the cable coming through the firewall, and then the whole mass is wrapped (rather neatly) in about 10 rolls of electrical tape. At, or rather below, the passenger side taillight, a subset of the wrapped wiring peels off to the driver's side. The tape goes to just a few inches before the taillights.

I've checked the grounds, by unplugging them one at a time, at the rear of the car, and they appear to be good. I checked both sides of the fuse box (inside and out), and have voltage there. I replaced both Fuse 1 and 2 with new 25A fuses.

I'm thinking the next step is to check the brake light switches on the master cylinder and make sure I have voltage on both sides. If I do, then I must have a break in the wire somewhere between the front and back of the car.

As far as I know, the brake and backup lights were working before this week, but then I really don't know. They may have been broken for months...but I kind of doubt it. As I said before, the only thing I did was give the car an overdue bath, including the back deck and floor. I didn't touch thew wiring though, plus at that point it's inside a rubber cable.

I did check the bulbs on the passenger side. Guess I'd better check the driver's side as well to be sure.

Sat Sep 02, 2017 6:22 pm

It definitely makes it a challenge to have modified wiring especially if the wire colors are different than stock. I think after you check the brake light switches, if you find them to be okay you might want to check the point in the harness in the engine compartment where the brake light wire splits off to the left and right side, and the same with the back up lights. It would be interesting to see how those wires are all connected.

Once you have the junction of the brake light wires exposed, you can do a continuity test from where the brake light wire starts at the brake switches to where it ends at the split. Am I making myself clear enough?

Sat Sep 02, 2017 7:51 pm

Yep! I appreciate your insights.

I did check the bulbs in the driver's side taillight, and they are good. You are right; it will be interesting to cut away the electrical tape and see how things are connected. My money is on a poor connection either where the wires split after the fuse box or back in the engine compartment....most likely the latter.

Sat Sep 02, 2017 8:15 pm

BlissBignall wrote: My money is on a poor connection either where the wires split after the fuse box or back in the engine compartment....most likely the latter.
My thinking exactly. Good luck!

Sun Sep 03, 2017 2:39 pm

Not sure about the backup lights but there is a connector inside by the brake fluid reservoir that I've bumped twice and lost my brake lights. A bugger to get to, I've used needle nose pliers to push both ends in and give a squeeze to get it connected again.
Good luck!

Mon Sep 04, 2017 11:40 am

So, I got down where I could see the master cylinder (recently replaced by my mechanic), and discovered he forgot to reconnect the brake switches! Could it be that easy? Of course not! Once reconnected, there was no change. I'm back to thinking it may be a bad connection or broken wire somewhere.

I'll check that connection inside too.

Thu Sep 07, 2017 11:37 am

Backup lights,

I've had fun with those, the "cigar shaped" fuse holder was behind my carb connected to the coil, shorted out once, the spade connector touched a metal tab for the wire harness that's on the doghouse and killed the engine and smoked like crazy.

On back of the transmission is one connector for that cigar fuse holder the other on my 73' thing was on the coil.

In my case before the fuse popped, it was a very dirty transmission connection and a burnt fuse.

Since then I've made adjustments so the short issue wont happen again.

hope that helps locate and get the reverse lights working.

On brake lights, I've heard the M/C pressure switches can go bad, you can in some cases stop the car and not get brake lights, mine work but I can press the brake pedal slightly with no light activation but they do come on when doing a full stop.

T

Sat Sep 09, 2017 6:04 pm

I found the culprit for the brake lights. It was the plug next to the brake fluid in the passenger compartment. Thanks KenJ06!

Now to figure out the backup lights....

Sat Sep 09, 2017 6:22 pm

BlissBignall wrote: I found the culprit for the brake lights. It was the plug next to the brake fluid in the passenger compartment. Thanks KenJ06!

Glad I was able to help!

Fri Sep 15, 2017 10:10 am

It's looking like my 74 Thing was not equipped with backup lights (which would explain why they wouldn't work). My mechanic is retro-fitting them now, but has anyone heard of Things not having backup lights?

Fri Sep 15, 2017 11:04 pm

The '73 German Military Thing I had did not have the transmission "switch" and had the small bus style lights...so no back up lights.

Does yours have the transaxle "switch"? I guessing your '74 has elephant foot lights...weird....then it should have the switch...or not....

I ran a manual switch to the European Fog Light and made a clear cover for it, (they are normally red) and then when I swapped the transaxle for a new one put in the correct wiring.

Mon Sep 18, 2017 12:26 pm

I have the "elephant foot lights" put on by a previous owner. The wires from the backup lights go nowhere. My mechanic searched all over the transaxle and transmission for where to put the backup light switch, and there wasn't even a place for it. I'm guessing vehicle inspections will just be entertaining.

Mon Sep 18, 2017 8:32 pm

the switch goes into the nosecone, I've seen just a plug there that looks like a bolt on some transaxles. The bolt comes out and put a back up light switch in...maybe...

Guess the Fully Restored Thing..was missing a few things. ;-)

Tue Sep 19, 2017 11:20 am

"Fully restored" is a relative term...Maybe I should change that to "Daily driver that stops when I push the brake pedal"