Intermittant Brake Light Problem

[ggunder]

I have a '72 with a brake light problem on the driver's side. It does not do it all the time, but sometimes it will not light up when the brakes are applied. I know the bulb is fine. Oddly, it seems to fix itself after I turn on the emergency flashers. I suspect a poor ground, but have not been able to find where the ground to the body is located so I can clean it up. The circuit diagram shows the ground somewhere in the passenger side rear of the car. Anybody have any thoughts on this? Thanks so much!

[ggunder]

I might as well come clean and admit that I took apart the turn signal switch not too long ago. Judging from some other posts, maybe that is that problem and not a ground. I have also noticed lately that sometimes the turn signal switch does not actually turn on the signals, another sign of switch problems. Hope I can figure this out soon!

[SteveJ]

I have a '72 with a brake light problem on the driver's side. It does not do it all the time, but sometimes it will not light up when the brakes are applied. I know the bulb is fine. Oddly, it seems to fix itself after I turn on the emergency flashers. I suspect a poor ground, but have not been able to find where the ground to the body is located so I can clean it up. The circuit diagram shows the ground somewhere in the passenger side rear of the car. Anybody have any thoughts on this? Thanks so much!

The brake light circuit goes through the hazard switch.

Hazard Switch ? Brake Light ? Turn Signal Circuit Analysis | Fiddling With Z Cars

The hazard switch may need to be cleaned.

Early Hazard Switch | Fiddling With Z Cars

[ktm]

The brake light circuit goes through the hazard switch.

Hazard Switch ? Brake Light ? Turn Signal Circuit Analysis | Fiddling With Z Cars

The hazard switch may need to be cleaned.

Early Hazard Switch | Fiddling With Z Cars

Technically, the hazard switch only provides power to the brakelight circuit. The power comes from the fuse block, to the hazard switch, to the brake switch at the pedal, then to the combo switch. If he is only getting power intermittently to one side, it is not the hazard switch.

Edited November 24, 2013 by ktm

[SteveJ]

You're right. I missed that. The turn signal switch would account for that better.

[Mikes Z car]

I purloined this drawing from a nice gentleman who made it. It is for the earlier 240z switch. I believe I read that later (1972) 240Zs have one contact on either side where this earlier switch has two adjacent contacts. If the driver brake light and a turn signal don't work I am thinking each problem is being caused by a different contact so that there are two problem contacts. Does that seem reasonable?

[ktm]

I have a 1972 240z and I have two adjacent contacts. Now that does not mean that my turn signal switch is original, but I do have two contacts.

I do agree with Steve and Mike that it is most likely related to the turn signal switch, more specifically the contacts therein. You'll probably need to disassemble the switch and clean the contacts. Corrosion wreaks havoc. I had an issue 6 months to a year ago that was related to corrosion on the contacts (passenger side).