I'm just going to vent out of frustration here LOL.... I'm in the process of stripping my firewall to repaint. I have a fuse block mounted on the driver's side wall. I replaced the fuse box with a newer, cleaner looking one and made every precaution to replace every wire exactly the way it was. Now, I don't have brake lights or headlights? Of course, my headlights were always weird in that I would have start the car to make them come on? Not sure where to look first? Any suggestions. Can I run the wires without using a relay? or bypass the relay, if there is one? I know there are one yellow wire and one white wire coming from each headlight (I'm guessing lowbeam and high beam) total of four wires. to the headlights. STRESSS!!!!!!!!! Ha ha ha...

 

What year/series is the truck?

Sounds like a p o wired the lights thru the ignition switch instead of steady power like they should have been.

Do you have a shop manual? Tracing the wire colors back to the fuse block with a wiring schematic should sort most of it out. It just takes me hugh amounts of time and patience. Hang in there!

 

I have a manual, however the original wiring is no longer there. It's a 56 F-100. The light switch is also not original. I'm going to have to trace the wiring and see what's going on. Patience is the virtue here LOL....... Thanks for he reply. I'll let you guys know what I found. Not sure if I'm going to wire direct? or use relays? Any recommendations?

 

If you use a large enough wire a relay shouldn't be needed. If you are adding driving lights or something then use the relay. Sounds like both your brake lights and headlights used the same connection. Find the missing wire and connect it to full time power to have the lights work as they should. Do your turn signals work? If so, then it should be a power supply problem. Trace wire up from mastercylinder pressure switch. One wire goes to lights, other wire is the power supply.

 

56 f600, thanks for the info. I think I'm going to try to get it to work without relays like you said. The turn signals are working. I think your right about the power supply. I'm only running the headlights, no running or fog etc. I'm going to be hanging out in the garage tonight to find out what is going on. I'll let you guys know what I find. Thanks again all.