Interesting electrical conundrum

[Less Than Joe]

So my left blinker was acting up last week, it would blink randomly and very dim/short. So I figured the blinker was going bad, after 12 years of service. So I replaced it, and everything worked fine.. for a few days. I pulled into my parking spot on day and my neighbor told me my brake lights didnt work. Sure enough, blown fuse. Figured, well, 12 years of service... replaced fuse, brakes lights work again. But...

Now, whenever I turn on the left signal, everything in the back flashes. Left signal, right signal, even the third brake light flashes. If I step on the brakes, everything stays lit and stops flashing. I've cleaned out the bulb sockets and checked fuses, everything seems in order. The right signal works fine as it should.

Ground....? or something might have crossed behind the fuse panel...? ugh.

[Mechman71]

Sounds like you've either lost the ground in the taillight or you have a short in the harness. First try the ground - take off the housing and clean up where it contacts the body. If that doesn't do it, unplug the taillight and plug in a test light and see if that works better. If it does, the problem is in the taillight. If not, it's further up the harness.

A corroded bulb base or socket can cause this, too.

[Gasturbine]

Replace your bulbs first. Its common for a broken filament, to drop down across another circuit within the bulb.

[Karma]

HI,
Hmmmm. Have you done any recent work on your electrical system? If so, what did you do?

Very often on this forum we find out later that the seemingly simple OP's original question/problem is a result of other work but we were not told about it at all. This drives me nuts.

Sparky

[Less Than Joe]

Checked all the bulbs and cleaned the sockets, everythings in shape back there. No recent work besides changing the flasher and the fuse as listed above. That's why I'm puzzled. It would make sense if I was playing around with the electrical system.

[Less Than Joe]

Took off both housings, all bulbs, checked connections, etc. No help. I put the old flasher (that wasnt working a few weeks ago) back in, and it turns out:

The old flasher was never bad, it just couldnt handle the load of trying to power all of the lights. The replacement flasher I bought was high load (for trailers, etc) and has the power to light all the back lights. So the problem was never the flasher, there has to be a short somewhere. But where, oh where is it? It's only the left signal, but why the hell are the brake lights tied into it?

[wildtyphoon]

ive seen a problem similiar, before on an old chevy truck. i cant rember the exact symptoms only that it didnt seem to make any sense because brake/turnsignals would light at times that didnt seem possible.

anyways long story short, it was a bad turn signal switch. thats the only place all those circuits come together in the same place.

[PBarrick]

If you haven't changed your rear bulbs do so before doing anything else. I know you checked them numerous times so far. I ran into the same problem and changed multiple items only to find my right rear buld contacts had become hot and were causing a short. Bulbs are cheap.

[Less Than Joe]

Changed the bulbs, no help. Also, I looked thru the wiring diagrams and such and have figured it has to be the turn signal switch. Luckily I have a spare one at home in the garage, so it just has to wait until winter break comes. Sucks I have to drive 2 hours home, making plenty of left turns.

[Less Than Joe]

ive seen a problem similiar, before on an old chevy truck. i cant rember the exact symptoms only that it didnt seem to make any sense because brake/turnsignals would light at times that didnt seem possible.

anyways long story short, it was a bad turn signal switch. thats the only place all those circuits come together in the same place.

Yea, It doesnt make much sense how those circuits would connect, but your right, it seems like it would be that switch. Gonna check it next week sometime when I head home.

[Mechman71]

The next thing to do is break out your test light, then disconnect the left turn signal feed wire and brake light wire from the taillight socket. Turn on the left signal and see if the brake light wire is getting juice. If it is, follow the wire up to the rear harness connector and separate the connector, then test the dash side of the connector.

If the brake light lead is still hot on the dash side with the rear harness disconnected, the problem is probably in the switch. If it's only hot with the harness connected, it's in the rear harness. If it's only hot with the taillight connected, it's in the taillight socket.

[Less Than Joe]

The next thing to do is break out your test light, then disconnect the left turn signal feed wire and brake light wire from the taillight socket. Turn on the left signal and see if the brake light wire is getting juice. If it is, follow the wire up to the rear harness connector and separate the connector, then test the dash side of the connector.

If the brake light lead is still hot on the dash side with the rear harness disconnected, the problem is probably in the switch. If it's only hot with the harness connected, it's in the rear harness. If it's only hot with the taillight connected, it's in the taillight socket.

There's only one light bulb that lights up both for braking and for turning, with one wire leading to it. I'm almost positive its gotta be the turn signal switch. I'll be able to test it with the spare I've got without tearing apart the steering wheel.

[Mechman71]

Ahh, sorry then! I work on so many different makes, I sometimes forget the specifics. :)
It's good that you have a spare switch and can test it first. The worst part of changing them is (of course) getting the $@#&!! steering wheel off. I've broken pullers on Jeeps before. Then again, both my original wheel and the leather wrapped one I sourced from a Cherokee practically fell off...

[Less Than Joe]

Just thought I'd add the solution in:

Took the steering wheel apart to add the new switch in, and luckily enough it was something I had guessed went wrong. My turn signal had stopped canceling when turning right, which meant the little spring inside had broken. Well a piece of it that broke off was lodged between the contacts for the switch. Just removed it and the switch worked just as it had before. Saved myself some money and a real hassle. Phew.

[Joe Dillard]

Cool! :coool: Glad to hear you got it tracked down. I hate pesky electrical problems.