Hi there, basically ONE of my brake lights isnt turning on upon application of the brake pedal (driver side). I thought it might be related to a bad headlight switch or bulb, but after replacement it still isn't turning on. However, when the headlights are on the other part of the filament does turn on (so pushing the pedal still doesn't do anything on the driver side). I have already cleaned the part the bulb attaches to, and I inspected the wire for cuts or openings but saw none. The passenger side works fine, and this problem came out of nowhere. I looked at my fusebox and none looked popped. I am out of ideas, hopefully someone has some?

 

So you replaced the bulb? Get a buddy and a multimeter and check to see if power is getting through when pressing the pedal.. If not, time to start tracing wires..

 

Does the turn signal work? Seem to remember that the routing of the brake switch passes through the turn signal switch.

 

I don't remember it being routed that way in the 66 but I can't remember for the life of me right now... I just did the tails like 6 months ago too.

 

trexgawd: the turn signals still work. I was driving one night and all my lights went out except headlights. Then, the next day, the problem im having now started. I replaced the bulb and I needed to do the headlight switch anyways so I bought a nice motorcraft replacement and installed it. Basically one filament in the bulb is lighting, while the other isn't. However this came out of nowhere...I'm looking for exposed wiring causing a short or something, or a severed wire somewhere. But I know next to nothing about troubleshooting elec systems.

 

I realized I wasnt clear on a few details right there. The day after all the lights went out, they worked normal again EXCEPT for the problem I'm still having (the filament thats supposed to light up upon application of the brake pedal is not lighting up).

 

And the passenger side brake light comes on?

scoothcu you're right it does route through the signal switch I just checked..

If the signal comes on and the passenger brake light comes on there's no reason the brake light on the driver side shouldn't come since they're powered by the same unit unless the contact is broken on the signal switch for the driver side and not the passenger side.. Take apare the turn signal switch assembly and look.

 

Just to be clear, you're saying that the brake lights are somehow related to the turn signals? The signals are working. The passenger side brake light is working fine. The driver side lights up when you turn the headlights on, but the brake light doesn't turn on upon application of the pedal, regardless of whether or not the headlights are on.

 

They may be different in your 69 but I know that in the 66 they are linked together.. When you press the brake it routes to the signal switch which goes across two jumpers that lead to the rear lighs (one driver, one passenger).. These would be the same wires that would carry the turn signal power.. So if the turn signals light up then it's not the wire, if the passenger brake lights then it's not the brake switch sending the power to through the signal switch.. It has to be something inside the signal switch, a bad jumper/connector for the driver side light..

 

Those turn signal switches are notoriously buggy. Sometimes the contacts wear and sometimes they melt and recess into the plastic. If your turn signal works it means the wiring is good from the front to the back. There's a problem in the area of that switch, if not the switch itself I would bet.