Ive run into a heck of a brake light glitch.

My brake lights do not come on.

1. The tailights work when the parking or front headlites are on, but the brakelights do not. With parking lights or front headlights off, brake lights will not come on when brake are applied. So it seems I have a problem somewhere in the breaklight switch circuit. Turn signals work fine wether headlites are on or not

I disconnected the brake light switch, and found it works fine thru a continuity check.

Now let me add this before the no brake light thing. 2 weeks ago, my drivers side outboard tailight would go dim if the headlites were on, and I applied the brakes. Just by chance, I was checking that brake tail/light housing this Saturday, and I accidentally grounded it against the rear bumper, a viola!, it worked fine, which makes the problem a poor ground. So I grounded it from the rear of the tailite housing to the frame, it worked fine. I didnt drive it anywhere afer this

So the next day, I walk out, and apply the brakes, and only the drivers side brakelights go on! Passenger side has tailites, but no brakelights!

Then magically, it progressed to no brake lights at all. Now I have just tailights if the headlites or parking lights are turned on. Turn signals work fine wether headlites are on or not. No brake lights at all

Man, my wiring under the dash that feeds the brake light switch circuit is so patched up with inproperly colored wires, there is no way I can trace where the problem lies

I beleive its a ground problem. But I have cleaned all ground straps, tailite housing grounds, etc, etc...........

One problem lies is that the wiring chart (Lectric Limited Laminated Poster)I have is very user unfriendly.

Could someone draw up a simplified (very simplified) wiring diagram (on power point maybe)that shows a simple brake/tailight circuit, that would show:

1. From power source to brakelight switch.

2. From brakelight switch to the 4 tailites/brake light housings, and to ground

(Remember, in my year (1968), back up lights are NOT in the tailight assemblies so I dont need the back up lamp circuit).

If you would please send to melvinjo@soc.mil

I may have to just compleley rewire to whole circuit. Cant afford a new wiring harness, and I cant trace the wiring because its so pacthed up

 

I can't supply a circuit diagram for your 1968 but there is one other part to the circuit puzzle that you may not have taken into account.

From the brake light switch, your wiring should lead up and into to the steering column. The hazard warning and turn signal features are all included in the turn signal switch inside the column.

I am not sure how you are going to do this but if you could find another turn signal switch, just connect it in place of your current switch and see if things operate correctly. Otherwise, you should try checking continuity through the current switch.

 

Im not sure what you mean by checking continuity on my turn signal switch? If the turn signals work, which they do, how does this play into the brake light circuit?

Are you saying the turn signals a brake lights work together in the same circuit?

 

Turn and break lites are the same filament of the blub. When breaks are on, both lite up, but if turn signal is also on, that one blinks off & on. He's saying if all else checks out, then the turn signal could be causing the problem due to it's override capabilities.

 

Ok, I got ya. Will do. Unfortunately, I dont have a spare turn signal swicth to check it againstc

 

See if you can diconect the wire harness at the base of the column and then retry breaks, maybe that will tell you if the breaks will work alone.

 

Henry,

If you can, please send a diagram. I really beleive Il have to wire this back up on my own

Ill try disconneting the harness as you said. I beleive I did that once by mistake, and they still didnt work. But Ill try again

 

If your directional filaments work fine, then your ground is good for your brake light filament(s) as well since they are the same filament as noted above. This points to either a faulty brake switch, or a faulty turn signal switch.

In its neutral position (signals off), the turn signal switch allows current to flow through the brake switch to the bright filament(s) (which are also used for the turn signals) when you step on the brake. When the turn signal switch is "on" (left or right turn position), the turn signal switch "de-selects" the brake light circuit and activates the turn signal circuit through the flasher. So... the turn signal switch can cause the brake lights to fail. Check the actual brake light switch (at the brake pedal ) first.

Tom

 

The brake light switch works. What I did as well, is I jumped the brake light switch wires, therefore bypassing the swicth to ensure the swicth was good after a good continuity check

Looks like I need to check my directional signal swicth, (sigh!)

 

John, As I recall you replaced your brakelight switch not too long ago. Does the emergency flasher work ok also? MJ


[Modified by MNJack, 12:01 PM 10/28/2002]

 

Yep, I sure did replace the brakelight swicth a long time ago

I didnt think to check the emergency flashers

 

I found the following two turn signal switches:

Turn Signal Switch 1968 Telescoping Column 5698520 - Available through GM dealers - $86.00 List

Turn Signal Switch 1967 - Zip Products ES-210 - $49.50. According to their latest catalogue, I think this is the standard column switch.

 

Melvin, the only diagram I have is in the back of my '72 Haynes manual, which is not here at the moment. I think Tom454 is on track. You might try some searches on turn signal switches for more help.

 

Melvin,

I had a very similar experience. My problem was that my fuse was blowing any time that I hit the brakes. Everything else worked fine but not the brake lights. I spent hours trying to troubleshoot it (even w/ the help of the forum).

I finally gave up and brought it to the shop. It turns out the problem was as Jim Shea said. The turnsignal switch. Turned out I hide a short hidden in the column. They replaced the switch and VOILA... Brake lights.

Wish you luck!!

Tim M.

 

I had this problem years ago and tried everything. It turned out to be the turn signal-hazard mechanism inside the column.