Hello all, I just bought a 78 F150 and i am having electrical problems. I am getting 12 volts to the brake light socket when both bulbs are out but when I put one bulb in the voltage drops to 5v and the bulb won't light. As soon as I pull the bulb out the voltage goes back to 12v . Made new harness for rear amid still same problem.
Any help would be great before I just take it all out.
I just replaced the wiring from rear to firewall and still same problem.
Well I found the problem to be power drop from fuse box to brake switch. I ran an in line fuse from Batt to switch and everything started working.
Edited by Montiehall, 10 October 2012 - 07:35 AM.