I just bought an 88' TA. Obviously the previous owner has done some "wirin' work" on it because the third brake light flashes in unison with the left turn signal. Also, the left signal won't work when the brake is applied. Where should I begin looking to fix this? Thanks!

Bump

first determin where the left turn and the third brake light are tied togather, then seperate them. most likely in the trunk, under the rear pannel. the left turn is either yellow or light green, and I dont know about the 3rd brake light. could be melted wires also? the harnes travels down the left door sill under the carpet,on these cars I believe. let me know and I can check a 92 Camaro vert parts car I can check.

The rear left turn is yellow, right turn is dark green.
The center high mounted stop light should be either light blue or could be possibly yellow (depends on year model etc).

If the problem is not in the wiring (either rear or under column), I'd suspect the steering column multifunction switch (aka turn signal switch - picture here). You can easily identify a bad switch by disconnecting it and depressing the brake pedal. Only the CHSL should light up. If the left rear turn signal lights up, it's in the wiring.

Hope this helps.
Lou

Thanks, Lou! Where is that switch located? In the column? When you say you can "easily identify a bad switch by disconnecting it", would I have to get in the column to disconnect it? Whew ... sounds like a job! But ... I guess if it has to be done ...

If you remove the driver side knee panel, you'll see the flat connector on the bottom of the steering column. Not hard to get to at all.

Lou

I'll try it this afternoon hopefully. Sounds like that should be the culprit. I hope so (sort of). I cringe at the thought of tearing the steering column apart, but at least I'll know where my problem lies! Thanks, Lou!

Hey check your grounds in the back (trunk) area. A Firebird I owned years ago did some wierd stuff like that and it just turned out to be bad grounding. 0 dollars to fix if you do it yourself, or maybe a few dollars if you need new wires. It was years ago for me, but I think it was something like my left headlight would come on with my right or left blinker . Some wierd crap like that. I took it to a auto electrical shop, and they ended up finding the grounds were loose or dirty or something. This was many years ago so I can't remember it clearly, but it won't hurt to check your grounds anyway, they do get dirty / loose/ rusty from time to time.

Update:

I disconnected the multifunction switch and the left turn signal lit when I hit the brake. So, I guess it's not the switch.

I also checked my grounds in the back of the car. Both of the ground screws are a little loose, and I can't tighten them. It's like the sheet metal screws get to a point and then won't tighten any further ... almost like they're stripped when you get close to tight. So, could this be the culprit? Something that simple? I hope so. I can throw some washers on there or replace the screws to see if that works.

Lou? Any ideas?

Sure, you can put some washers on the screws temporarily. If they hold, it's all good.
I don't think, though, that your symptoms are caused by a bad ground since those two circuits don't share a single wire once you disconnect the multifunction switch.
I'd really look into the wire hacking that the PO did. If the CHSL has a yellow wire, it would be easy to mistake it for the yellow left turn wire and splice them or something.

If you see yellow wires behind the tail lights, they can ONLY go to the tail bulbs, NOWHERE ELSE. That would be non-stock wiring and might explain the CHSL problem.

Let us know what you find.
Lou

Just replace the screw with one of a slightly larger diameter, and make sure you're not overtightening them, they strip out easily as you've now seen.

Yep, what he said. Even if it's not the culprit, they need to be fixed. And BigBabyLou, not trying to knock your advice at all, sounds like great advice and knowledge. Just wouldn't want to see anyone go through a lot of work, and some money to only find it was a ground.

This makes sense. I'll fix the grounds anyway just because they need to be tight. I'll look for some "yeller" wires tomorrow. Thanks, guys! I'm a complete novice when it comes to vehicle wiring.

91RedRagtop ... nice ride!

I was just about to say the same thing to you.

I agree with checking all the grounds. Strange problems like that almost always seem to be tied to bad grounds. I had a '90 Trans Am once that's headlights would pop up every time you hit the brakes. It turned out to be a bad ground on the tail light harness.

As suspected, the grounds are not the culprit. I replace both grounding screws (originally 8 - 1/2) with two 10 - 1/2 sheet metal screws. They cinched down tight, and all contacts were clean.

There is a yellow wire with a black stripe that runs to the block on the bottom of the contact panel that powers the third brake light. Could this be it?

Oh, your CHSL is powered through the contact plates, that's the right wire then. Make sure nobody spliced it into the other yellow wires in the tail light harness. Just follow the harness into the left wheelwell and if needed even more forward into the cavity behind the LR speaker and down to the floorboard by the driver side door (under the plastic door sil).

It might not be an intentional splice, it could be a simple screw driven through the door sil into the wire bundle, shorting the two wires. Just as an example.

Hope you find it soon.
Lou

Well, the carpet is getting replaced as soon as the new carpet arrives, so I've got to tear out the interior anyway. Hopefully I'll find it then. I'll post up and let you know when I do. Thanks for all the help! At least I don't have to tear apart that darn column!!

OK, so I finally got a chance to fish around under the dash a bit today, and I discovered something worth noting. It is a lonely yellow wire that comes out of the column with no home. Could this be my problem (or point to the problem) with the brake light and tail light?

Can you trace the wire to its origin? It would tell us more about it.

Lou

It goes into the column. Beyond that, I don't know.

Also, the PO installed some sort of aftermarket alarm along with remote start and keyless entry if this helps diagnose anything.

i think its at the other end. the 3rd brake light should not even be connected to the turn signal. i would guess that the wire into the brake light broke somewhere around where the rear trunk joins to the car in the back.
follow that wire down into the left hand side rear wiring bundle that goes into the rear where the stop and turn signals are. i vote for someone needing power to the 3rd stop light taping into the wrong wire in the bundle.
i vote for grid 35 c-e

Man, thanks for the schmatic! Now I just have to learn how to read the darn thing! Haha. I think the yellow wire I found has something to do with disabling the ignition for an alarm system?

Ding Ding Ding!!

Here was the whole problem. This was underneath the lock box.



The PO decided (for completely unknown reasons) to splice the left tail light wire and the center brake light wire together with this blue connector. Took the connector off, wrapped the wires in electrical tape to keep them from shorting, and voila! Lights work as they should.

I have no idea why he did this.

Damn, I hate to be right.
Glad you found it! I can't tell you why the PO would do this, it makes no logical sense.

Lou

glad you found it.
down load that diagram and keep it around in your computer it will come in handy.

Done. And printed . Thanks, guys!