I have been battling my brake lights for two days. I've had my 79 F100 for about a week now and I discovered quickly that if I changed anything to do with the electrical system, I had to take out the emergency flashers/brake lights fuse and put it back in to have brake lights. This no longer works. I have spent the last 6.5 hours working on it and changing out a few parts and nothing has worked yet. For a while, everything worked back there but the brake lights. Now tail lights work, but not emergency flashers or brake lights. I am getting power to the switch on the brake pedal and replaced that switch this morning. I also replaced the flasher switch, but it was good to start with. I just figured I'd do it in case it might have some sort of fault. I've read lots of threads and none said the brake lights didn't work but the emergency flashers did (which was the case but is not anymore). I'm completely stumped at this point. Any ideas?

 

Have you checked all your grounds?

 

All of them that I could find. I switched steering wheels and that's when it started. Could something have gone wrong there. Could it be the turn signal switch doing all this?

 

Now I'm seriously confused. It's the driver's side that I'm having trouble with. I replaced that socket and bulb this morning and the driving light, hazard light, and turn signal work on both back lights. The brake light is the only thing that isn't working. This goes against everything I've read on this so far. I've read that if the brake lights don't work, the turn signal shouldn't work but it does. I'm starting to get frustrated.

To add insult to injury, I'm selling the car the truck replaced and someone today said he'd pay cash tomorrow for it but I have to have a vehicle to get to and from work.

 

Are both brake lights not working, or is just the driver's side not working?

 

Both brake lights aren't working. I'm stumped.

 

How does the fuse holder look? Fuse fits nice and tight and the connections on the holder are good? I own some pinball machines, I've seen weird problems from a bad holder.

 

Did you check the ones behind the taillight assemblys?

 

If it is just the brake lights, did you check the switch on the brake pedal? Maybe it got disconnected or out of adjustment when you messed with the steering wheel.

 

The signal goes from the brake switch to the turn signal switch. That is how the brake lights get pulsed when you have the brake lights on. The turn signal switch very well could be suspect. I had an old Chevy truck that would only turn the brake light on to the side that the switch was last moved to. Never could get both at the same time. The switch needed replaced, but it was such a pile, I didn't want to blow the money on it, and lived in mostly rural area.Also have a similar situation with a Neon, except it just lights the turn signal indicator in the dash. The old switch actually would cycle the flasher, but it wouldn't go anywhere but the flasher, just could hear it clicking real fast. Changed the switch and the flasher stopped that. My bet is on turn signal switch being your problem.

 

Thanks for all the replies. I replaced both sockets for the tail lights and cleaned the grounds there. Now I have the passenger's side brake light working (to be honest, it might have been working yesterday. It was bright outside and my wife was busy so I had my kid helping me look at it and I know the light was dim). I ordered the turn signal switch from LMC Truck so hopefully I'll get that in really soon. It looks like it'll be a pain to switch out but hopefully worth it.

 

The hardest part generally is getting the connector passed through.

 

Will it pass through? That would probably help a lot. I know it looks like a very tight fit.

 

You have to turn it lengthwise, it will not pass though full width. It is tight, but will go through.