Brake lights not amplifying… HELP!

[ballajim123]

Thanks for the add to this forum! Long time lurker here. 1968 Bronco. Original wiring.
I need help with my brake lights. Situation is this: brake lights come on when brake pedal depressed and no tail lights on. But when I turn on tail lights and depress the brake pedal, there is no amplification of light. It’s just normal tail light brightness. I’ve replaced brake light switch and same symptoms remain.

 

[BroncoLew]

Do your turn signals work as well?

 

[ballajim123]

Yes, turn signals work

 

[laserfish]

Check and clean all grounds. Always a problem.

 

[DirtDonk]

And when the turn signals are flashing, they are bright. Correct?
Has the vehicle been painted? If not, how rusty are things in general?
The tail lights ground through the two screws into the body. Make sure the holes are clean.
If the little plastic insulators are still there, that’s great. The housings don’t actually ground through the painted metal very effectively anyway, and those are for keeping corrosion down and for protecting the paint.
The sockets can become corroded and the contact points even bent a little to the point where something doesn’t work. But at this point, if we know your turn signals work, then the brake light circuits are intact because they’re the same filament. In fact, they’re the same wire all the way from the turn signal switch to the tail light.

The brake light switch was never at fault at all, because you said that they worked when the tail lights were not on. So don’t throw away your old switch because it’s still working.

Does your 68 have hazard flashers? It should, so check to make sure those work.
Then see if they work with the tail lights on. If they are flashing, press on the brake pedal and see if they stop flashing.
The brake signal overrides the hazard signal.

 

[ballajim123]

Thank you DirtDonk! I've ordered a new set of taillight housings and I'll check out the ground connections prior to them arriving. Thought it might be a good idea to have fresh sockets in play.
The bronco has been painted by previous owner (shotgun) so I don't expect the painter taped off anything that required effort. No rust, thankfully
I am not sure on the hazard - will go check that now

 

[Broncobowsher]

FYI, some of the new tail light sockets are wired backwards. Running light is bright and brake light is dim

 

[ballajim123]

Still battling! Installed the new tail light housings and LED panel. Much brighter! but still no amplification on brake lights when running lights are on. Turn signal is much brighter. Is the turn signal the same brightness and brake light?

 

[Yeller]

Yes they are the same, they use the same element.

I’ll ask a dumb question…. With all lights off do your front lights come on as well with the brake lights? Do the brake lights work with the turn signals on?

 

[ksagis]

My guess is wiring is jacked someplace in vehicle. Suggest you wire 12 volts directly to temp installed light and see what brightness is what. Maybe when park lights are on, its feeding power to brake light circuit versus.

Another idea, my tail light housings were older and the “crimp” contact between the bulb socket and housing wasn’t great anymore. I soldered a jumper across them to the tail light body ground for a temp fix (which is still in service two years later)