Brake lights stopped working - '39 Fordor

moonraker

moonraker

Senior Member
Can you guys tell me where to start looking? They worked fine after complete re-wire of the car. Not any more. And it looks like if I depress the brake pedal while parking lights are on, parking lights dim a little. Any ideas?
 
.Pull the wires off the brake light switch and with the power on touch them together and see if the brakes lights come on.Verify that all ground connections are good.Body to frame,motor to frame etc.
 
deuce lover said:
.Pull the wires off the brake light switch and with the power on touch them together and see if the brakes lights come on.Verify that all ground connections are good.Body to frame,motor to frame etc.
Click to expand...
Thank you!
Does the brake switch connect the light to the ground or to the hot side?
 
moonraker said:
Thank you!
Does the brake switch connect the light to the ground or to the hot side?
Click to expand...

On an original switch at the master cyl you have 2 connections .One wire is hot and the other wire goes to the brake lights.Just pull wire off and touch them together (and see if brake lights come on)with the ign on.Should have power even if ign is off I think.Mast cyl is bolted to a bracket which in turn is bolted to the frame so that is the ground.
 
The tail/stop lamps have the ground path. The switch deals with power switching only so don't attempt to ground any conductors in the power circuit. Just be sure the tail lights are well grounded at the appropriate place/places. I use alligator clip test leads to test things but I would disconnect at least one of the wires off the switch terminals. A hydraulic type brake light switch would have a ground at the body but should be isolated from the ground at both terminals. It's just an on/off switch. I've replaced many of the modern replacements over the years. The old original parts were pretty reliable.
 
Also, the brake circuit is hot all the time, so ignition switch or light control switch position should not be a factor. As already stated, start with the brake switch. If not the problem next most likely issue is the ground at the brake/tail lights. All of this assumes no turn signals! If you have TS installed there could be other issues.

Just a side note, turning the ignition switch on during trouble shooting can lead to serious ingition issues, so be sure you understand what's going on there!
 
If you have stock switch and are using DOT 5 brake fluid, that could be your problem. DOT 5 gets behind the diaphram and lets the smoke out. Use a Harley Davidson stop switch ( they use DOT 5 fluid) and your troubles should be over.
 
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