So, walking out towards the back of my truck in the parking lot yesterday, it looked like my parking lamps were on. They were not on. They were brake lamps. After fiddling with the switch some and tightening the lock nuts, they went out. I assumed it was working properly. turns out, i had it tight enough to push the switch, which turned off the lamps. After getting home, I discovered they were stuck on again. I did not tighten the switch enough by hand to hold it. When I applied the brakes, or manually pushed the switch button, they went out. This is a newer switch. With the switch disconnected from the terminal, the lamps were out. +12 volts on one leg, tested with multimeter. I used a jumper wire to the two terminals, and the lamps came on. What I don't understand is that the switch has continuity when connected, but not when the switch is depressed. This seems backwards to me. Seems the switch should show continuity(closed) when depressed, and open when not depressed. I read this thread: Turn and Stop Lamp Diagnosis for 70's Ford Pickup - Ford-Trucks.com
which stated it is open when depressed. This baffles me. When the circuit is complete between the two wires in the terminal, the lamps come on. So it only makes sense for the switch to be naturally open, so the circuit is not complete and the lamps stay off, then the circuit closes when the pedal depresses the switch and the lamps come on.

Please tell me what I'm missing here. I checked and have continuity between the two terminals of the switch, and not when depressed. I even went to the parts store with my multimeter to confirm the new switch is the same, which it is. I have checked my grounds and all are clean and secure. all turn signals work properly, hazards, headlamps, etc. I have a 1978 F150 4x4 4spd. Aftermarket steering wheel with original turn signal switch. Any suggestions on what to check?

 

The switch works backwards from what you think. It is depressed (open circuit) when the pedal is in the up position. When you press the pedal, the switch is released to the closed position. So if the lights are staying on, adjust the switch so the button is pushed in farther with the pedal in the up position.

 

Ah, so it does, LOL. I feel like such a dumba$$ for not looking at that more carefuly. I was even the one who installed the switch last time... Makes perfect sense now that I looked at how it mounts to the stationary bracket, not a bracket attached to the pedal assembly. Thanks a bunch.