I have an interesting issue with my brake lights that I would like a little input on from you guys and gals.

I have a 1978 F250 4WD that I am getting up and running. While checking lights and bulbs I noticed I didn't have a passenger side brake light (Driver's side is fine).
- Checked the bulb - it's fine
- Checked the current with a circuit tester - no current
- Checked the turn signal - works. (both turn signal and brake light share the same wire, so wire appears to be alright since turn signal works.
- Rechecked brake light again - no power
- Pierced the green wire with a tester light and I get pulsing turn signal only.
- Checked wiring plug and I'm getting electricity for all except passenger side brake light

So what I know - electricity is passing through the wire because I am getting turn signal - just no brake signal.

After following the "282 Gr" brake light wire on a wiring schematic, I find it runs to the turn signal switch. The switch does not cancel so I was planning on changing it anyway, but is my thinking correct - can my brake light issue be related to the turn signal switch?

 

Yes it can be.

After the Brake light switch (On the Pedal) it's first stop is in the turn signal/hazard switch(es) assemby. From there it separates into Left/Right Turns and Stop, Kinda like a trailer plug setup.

See if you get volts at the under column Connector? Ohm from there to the back if you hafta.

 

Dave....awesome explanation. That makes total sense I will check that connection. Didn't think about that end of the ground

 

at the risk of beating a dead horse - also check all of your grounds. I had exactly the same symptoms a few months back and discovered that while the ground wire was great the actual socket-to-ground-wire connection was crap... in the front turn signal socket. Replaced that socket for a few bucks and suddenly my REAR signals and brake lights started working right. Based on my limited experience over the last few decades, I would say that probably 90+% of what I originally thought were switch problems on old cars turned out to be ground problems.

 

2 of the best reads on this problem. https://www.ford-trucks.com/forums/1...ml#post1812190


Turn and Stop Lamp Diagnosis for 70's Ford Pickup - Ford-Trucks.com