The Stovebolt Site Forums The Shop Area The Electrical Bay Intermittent Brake Light Issue on 57 3100 - Results

Every so often (and possibly related to work being done), the brake lights on my 57 3100 just stop working. Sometimes, they start working again on their own. This has happened ever since I started working on the truck. Maybe I shift a ground or something while working and it fixes it for a while. I don't know. But I do know that every time I get into the truck to go somewhere where it matters that they work, they don't (as in the Devil's Backbone Brewery Tour this last weekend). Brake lights worked fine the day before, then the morning of...nothing.

Turn signals work. Recently installed a new aftermarket turn signal switch because my old SignalStat 900 shorted out and fried half the wiring under my dash (learned a lesson about fuzed power that day, so not a total loss). The brake lights worked fine after the install of the turn signal switch for about two weeks.


I have power at:

The line that goes from fuze block to the turn signal switch
The brake light wires themselves (turn signals work)
Tail lights

I have the tail light housings grounded to a clean, solid ground on a nearby frame crossmember.

When I fully depress the brake pedal and activate the switch, I get no brake lights. I have done this with running lights on and off, turn signal on and off.

I need to check for power at the brake light switch yet. Will do that tomorrow probably.

So, does the brake light 'system' get a ground from the housing being screwed to the bottom of the floor pan? My driver's side floor pan is a swiss cheese pile of rust-eaten former metal, so that may be part of the problem. But a switch being a switch, does it not just break the power wire?

Suppose I could direct ground with a temporary wire to the housing of the switch if that's where it grounds and test the lights that way. But with the tail lights already grounded, is this a silly exercise?

Any help is appreciated.

Jim

the only ground that's needed is at the lights, and if the rear lights work for the signals there isn't a ground problem, switches do not need grounds .... check the fit of the wire terminals on the brake light switch, they may be loose and oxidizing enough to be erratic

Bill

Could be a faulty brake light switch also.

Good ideas. Will start there.

Thanks Gents.

Jim

Jim, first try wiggling and pressing together the multi wire connector that's on the wires coming out of steering column, that plugs into the main harness.

I get what you mean, but I only have the horn wire coming out of the steering column. My truck did not come with turn signals from the factory.

But, I will double-check my connections of those wires where they join the wiring harness under the dash.

Thanks. Keep the ideas coming!

Jim

Well,

Tracing back the wires, I found that the hot side of the wire (round style terminal) at the switch was 'sorta' loose. Not especially, but enough to probably be the cause of my intermittent problem. Crimped down a little bit and they seem to be back to normal. Tracked back to the tail lights with no other issues found.

Good call, Bill, as always.

Thanks for all the suggestions guys.

Jim