No power to brake light switch
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5th Wheeling
Joined: Feb 2022
Posts: 25
Likes: 0
No power to brake light switch
Hi all,
I have turn signals and running lights, but no brake lights on my 71. I replaced the switch but realised there is barely a flicker of power in the wire to the switch, 0.01 to be exact. There is power at the 20a fuse (I think this is the one it powers), but the fuse box is a little corroded and dirty. The only fuse with no power is the 2a but I don't think this would cause the issue?
Not sure if the turn signal switch is to blame here, as I'm lead to believe there would be power to the brake light switch if this was the problem.
Any help appreciated guys, I'm desperate to drive my truck again after winter!
I have turn signals and running lights, but no brake lights on my 71. I replaced the switch but realised there is barely a flicker of power in the wire to the switch, 0.01 to be exact. There is power at the 20a fuse (I think this is the one it powers), but the fuse box is a little corroded and dirty. The only fuse with no power is the 2a but I don't think this would cause the issue?
Not sure if the turn signal switch is to blame here, as I'm lead to believe there would be power to the brake light switch if this was the problem.
Any help appreciated guys, I'm desperate to drive my truck again after winter!
Lead Driver
Joined: Jul 2017
Posts: 9,600
Likes: 1,174
From: San Jose, CA
Double check the diagrams for your your truck. Because until at least the late 70s I believe, Ford took the power for the brake lights directly from the headlight switch.
The turn signal and hazard fuse is a separate deal and does not power the brake lights. Even though they all go to the same place in the end, the fuse is before the turn signal switch.
This is my thinking, anyway, and all of the Broncos and, at least the mid 70s trucks. I’m pretty sure had power from the headlight switch.
Black wire with the red stripe (I think?), coming from the switch.
You might reach up and jiggle your headlight switch connector, or, test for voltage at your brake light switch while wiggling the headlight switch.
good luck!
The turn signal and hazard fuse is a separate deal and does not power the brake lights. Even though they all go to the same place in the end, the fuse is before the turn signal switch.
This is my thinking, anyway, and all of the Broncos and, at least the mid 70s trucks. I’m pretty sure had power from the headlight switch.
Black wire with the red stripe (I think?), coming from the switch.
You might reach up and jiggle your headlight switch connector, or, test for voltage at your brake light switch while wiggling the headlight switch.
good luck!
Cross-Country
Joined: Jun 2022
Posts: 63
Likes: 33
I had the same problem on my 1970, the fuses were good, but the ends had slight corrosion on them (I guess that can happen on a 50 year old truck). Pull you fuse and sand the ends, that cured my problem. Hope this helps.
Lead Driver
Joined: Jul 2017
Posts: 9,600
Likes: 1,174
From: San Jose, CA
That’s actually a very good practice for these old glass fuses.
I actually started doing it every couple of years in fact. First cars I ever dealt with or owned, we’re only a few years old at the time and just taking the fuses out, wiping them clean, putting them back in, and sometimes separating connectors and cleaning them and putting them back together, made everything work much better.
Didn’t even know I had a problem until I cleaned things and the functions got better!
So that’s one of those good general practices.
and even though it’s not really a big issue with blade type fuses, I still do it out of habit, even on those.
I actually started doing it every couple of years in fact. First cars I ever dealt with or owned, we’re only a few years old at the time and just taking the fuses out, wiping them clean, putting them back in, and sometimes separating connectors and cleaning them and putting them back together, made everything work much better.
Didn’t even know I had a problem until I cleaned things and the functions got better!
So that’s one of those good general practices.
and even though it’s not really a big issue with blade type fuses, I still do it out of habit, even on those.
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