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1967 - 1972 F-100 & Larger F-Series Trucks Discuss the Bumpsides Ford Truck

Brake light wiring question

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Old Jan 1, 2022 | 05:24 PM
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Brake light wiring question

I have the wiring diagram for the electrical system of my 72 f100, but I am done fooling with the brake lights. Only the passenger brake light illuminates when I press the brakes. When I turn on my running lights the brake light on the driver side stays constantly on as if I’m pressing the brake pedal even when I’m not. Ive followed the wires looking for bad grounds/shorts, replaced the switch multiple times at the pedal, and I can’t fool with it anymore.

My question is if I were to bypass the driver side brake light and just used the power from the passenger side which functions properly, where should I start and where is the easiest place to tie the wires together so both the left and right running and brake lamps work? I realize that that Will probably impact my turn signals but I need to have both brake lights functioning. Hopefully that makes sense.
 
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Old Jan 1, 2022 | 05:36 PM
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The turn signal switch is more than likely your problem.
 
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Old Jan 1, 2022 | 05:37 PM
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Originally Posted by Christmas
The turn signal switch is more than likely your problem.
that has been replaced and rechecked also
 
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Old Jan 1, 2022 | 05:48 PM
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All lights except the headlights run through it. Just because it's new does not mean it works.
 
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Old Jan 1, 2022 | 06:27 PM
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I didnt even put 500 miles on my 72 f250 and my DC turn signal switch already broke one of the recentering tabs. But, all the wiring does work.
 
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Old Jan 1, 2022 | 06:44 PM
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Originally Posted by Christmas
All lights except the headlights run through it. Just because it's new does not mean it works.
if thats possibly the case then which wire to that signal selector goes to the driver brake
 
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Old Jan 1, 2022 | 06:59 PM
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It's more than likely the contactors in the switch not the wiring.
 
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Old Jan 1, 2022 | 07:11 PM
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Have you confirmed that you have 1157 two conductor lights front and back? I've seen similar problems with bad grounds on the front or rear light housings or where single filament light bulbs were inserted into 2 filament housings. Both can cause brake light and/or running light problems.
 
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Old Jan 1, 2022 | 08:50 PM
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Originally Posted by GPatrick
Have you confirmed that you have 1157 two conductor lights front and back? I've seen similar problems with bad grounds on the front or rear light housings or where single filament light bulbs were inserted into 2 filament housings. Both can cause brake light and/or running light problems.
i know the brake lights are, but the front parking lights may be leds… perhaps thats causing a problem. Although, even when the front bulbs were not led, this was still an issue
 
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Old Jan 2, 2022 | 08:13 AM
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Matt, did you check all the connections where the wires exit the steering column and into the connector! I had one wire pulled from the connector somehow, while changing the master cylinder. That drove me nuts for a few days!
 
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Old Jan 2, 2022 | 01:49 PM
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Originally Posted by Dans72
Matt, did you check all the connections where the wires exit the steering column and into the connector! I had one wire pulled from the connector somehow, while changing the master cylinder. That drove me nuts for a few days!
thats where I started because I though maybe something was bound, but I didnt find anything. Chasing electrical gremlins is the worst
 
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