I have a '60 F100. Left rear turn signal/brake lamp only work when lights are on. Lights off - no lamp or signal. I'm no whiz with the electrical stuff. Where should I start and what am I looking for?

I appreciate any help you all can share.

furyus

 

bad ground, bad ground, bad ground..

Sam

 

Well actually it could be two problems. In either case you have power flowing in or grounds being provided in the wrong place.

Sam could be right with the bad ground but only in that the lights are back grounding through the running light side of the bulb. The running lights and the brake signal lights are on completely different circuits and not related/connected at any point other than the base of the light bulb/ground.

Or you could have a short across the running light and brake/signal light wires.

A little background: your signals use the filimant in the buld and wiring that also lights your brake light. There are two power inputs to the brakes signals. One at the brake light switch on the master cylinder, the other inputs to the flasher. The running lights come straight off th eheadlight switch...and ne'er the two shall meet.

First thing I would do is pull th elense off the left rear light and clean it. Get a meter and check that there is a good ground from th eframe to the ase of the light bulb socket. (0Ohm setting)

Next take the meter and check that there is power (DC Voltage) flowing to the signal light/brake light contact in the bottom of the socket - with both brakes and signals. The meter woulld be set on the 50VDC setting.

If that's ok, you might have the wires flip flopped at the bullet disconnects back by the light.

Try tat and get back to us and let us know what happened.