Brake Light Issuse
 

Hello all. I have a 1979 F150
My brake lights aren't working. While doing a search on the topic I read in a thread that if the emergency flasher goes bad that can effect the brake lights, so I checked that but it seems to be just fine. The fuse doesn't look bad, and the hazard lights turn on so I'm sure it's not that. Couple other things I read that I haven't had a chance to get into yet, something about the cleaning up the four ground connections on each of the four corners of the truck, and updating the sockets. I'll clean up those grounds with a wire brush first thing. Any suggestion on the best type of socket to get? I bought new bulbs today and I recently replaced the brake switch that connects to the brake lever, it works just fine. Any other ideas of what to look for would be helpful. Thanks in advance.

You say you replaced the brake light switch and works fine?
So you have power going in and when pedal is pressed you have power out?
If so look at the turn signal switch as power out goes to it then out to left & right rear lights.
This is so when pedal is pressed and turn signal on the brake light does not work to that side.
Dave - - - -

FuzzFace, great question. I don't know for sure that I have power going in and when the pedal is pressed power going out. What would you say is the best way to check the power going in and going out? I have a test light and multimeter, but I'm inexperienced enough to know exactly where to do the testing.

If you have a test light, simply ground the pigtail and touch the probe to bare wire, both going into and out of the switch. Basically 12V current goes into the brake switch, and when the brakes are pressed it then goes into and out of the turn signal switch, thence to the rear to the actual sockets, through the brake light filaments, then out of the socket to ground. You should have juice to the switch all the time, and when the pedal is pressed both wires at the switch should be live. If so, great. The next easy step is checking the sockets, touching the probe to the little 'buttons' at the bottom of the socket - if you do not have juice there, your issue is somewhere between the pedal and rear. If you have juice at the socket, make sure the socket is actually grounding with your meter (sometimes the socket looks good but the ground connection is bad) and clean up the screw grounding point near the sockets. You can use the multimeter at every step I mentioned instead of the test light.

Thanks Dave. I'll look into that today. Any suggestion on how to engage the brake pedal if I'm working alone? Maybe just as simple as leaning something heavy against the pedal? I can get creative :)

First is to check at the brake light switch and if no power there no need to check out back LOL.
To check out back I would unplug the wire to the switch and use wire to jump it out so you can check out back.
I have a bunch of wires with clips just for this type of testing.
Dave - - - -

You make a darn good point man :-missingt

I normally just wedge a squeegee between the seat and the pedal, or a piece of scrap wood.

Yup, simple and effective. Thanks.

I used my test light on the brake pedal switch, power wires at the switch are live when the pedal is pressed. I wedged a piece of wood and held the brake pedal while checking the rear brake light sockets, no power. The rear running lights are getting power but not the brake light sockets. What's my next move?

Oh, I haven't checked/cleaned up the grounds yet. I'll do that now. Looks like this is the screw ground you'd mentioned.

Also, the sockets look really old. Would be worth it to replace them even if they're not the problem.
https://cimg6.ibsrv.net/gimg/www.for...cee8fd5fb.jpeg

Yes and no lol.
If it ain't broke don't fix it. But if they're old don't be surprised if they break soon (or 40yrs from now you never know) and you have to fix it.
So fix it now or fix it later. You got the time and money to spare fixing working parts go ahead, trying to save your pennies, just wait till it breaks.
IMO they are easy enough to get to that id wait till they break. <- again assuming like you said that they are not your problem

Understood. For now I'll wait to replace them until I need to.

Well I cleaned up the ground screw and all the contact points, still now power to the sockets. What's my next move?

If you've got power at the brake switch and no power at the socket it sounds like there is a problem with the wires. You can test for continuity from the switch to the plug... it should not be an open circuit with the brake pedal pressed.

Forgive me man, I'm new at this :o
Will you please be more specific with me about what plug you're talking about?
I know of the plug that the brake pedal switch plugs into, that plug has two wires that then go into the wiring harness behind the gauges console.