Flashing Brake Lights

[Michael M.]

Could use some help diagnosing a weird brake light problem on my '68.

When I push on the brake pedal the brake lights will come on for a millisecond and then turn off. After I noticed this, I paid a little more attention and determined that if I applied light pressure to the brake pedal, the brake lights would stay on no problem, but when I pressed harder on the pedal, the brake lights would stop working.

I immediately suspected the brake light switch on the brake pedal. I disconnected it from the harness and connected a continuity tester to it. No matter how hard I pressed on the brake pedal the switch maintained its continuity. So it seems like it's good.

I checked the connection of the switch at the harness and it is tight and all of the dash wiriing was replaced about a year ago with no problems until now. I've looked under the dash with a flashlight and can't see anything obvious like a loose wire or anything.

Is it possible that the brake light switch is still bad, it's just that it fails under load and not when being tested with a multi-meter?

Any responses/help would be appreciated. Has anyone experienced this issue before? Of course, the 68 brake light switch is a one year only item, so finding a replacement to do a simple swap to test the switch isn't such an easy proposiiton. Thanks and sorry for the long post.

[Stephen L.]

Re: Flashing Brake Lights

Try jumpering the brake light switch with clip leads. If the lights stay on then the switch is presumed bad. If the lights still won't stay on then trace the circuitry. I believe the circuit includes the hazard warning switch as well as the turn signal switch. You may try just cycling them a few times to see if they have a problem.

EDIT: The brake light switch is normally closed and held open when the brake pedal is not depressed. So you should see continuity (0 ohms) only when the pedal is depressed.

[Michael M.]

Re: Flashing Brake Lights

Thanks Stephen. I'll try cycling the hazard light switch and see if it helps. I've used the turn signal extensively during this period so no issue there. Good idea on the jumpering of the switch.

[Gerard F.]

Re: Flashing Brake Lights

Thanks Stephen. I'll try cycling the hazard light switch and see if it helps. I've used the turn signal extensively during this period so no issue there. Good idea on the jumpering of the switch.

Michael,

If you eliminate the brake light switch as the problem, and still have brake light problems, the next thing to investigate is the signal light switch.

The 68 signal light switch is the same as the 67 switch which I am very familiar with. (having replaced it 3 times). The particular switch was only used for two years.

On a 67 and 68, the brake light circuit goes up through the column to the signal switch which distributes the brake light signal to the rear brake lights through a little plastic cam. If you are having erratic brake problems, it could be that the contacts between the cam and switch are bunged up.

If you search the archives under 67 Signal Switch, you'll see quite a few posts on my trials and tribulations on the switch with pictures.

Cheers,

[Michael M.]

Re: Flashing Brake Lights

Thanks Jerry. I messed with it a little tonight and I think for some reason it was a loose connection at the brake light switch connector to the main harness. I bent the connections a little to make better contact and added some dieletric grease. All is good now. I sure hope the turn signal switch isn't bad as I just replaced it 6 months ago with an NOS one that I paid a pretty penny for.