53 f100 lights issue
 

Hi there, Just bought a great condition truck but it has lighting issues. the brake lights barely burn the filament, not enough to show thru the lens. I measured 3 volts. I jumped the brake switch to take it out of the equation, no change. i cleaned the connections in the splices where a prior owner added the back lamps, no change. I ordered and installed new 6 volt bulbs no change. Im not sure how/where they ground but that would be my next guess. oddly the tail lights and rear blinkers light fine....wouldn't they be on the same ground?

Secondly, I noticed the right front blinker was out, when I went to change the bulb, I noticed the socket pins were opposite the bulbs . . as opposed to : the front lights look original. Were bulbs from 1953 opposite as the ones they sell today??

Thanks!

Start with the ground. Clean the surface contact and the end piece really well. If it has any corrosion replace it. 80% of all electrical problems I've had on any vehicle where ground related.
How do your running lights look? If they're really bright it's possible the brake like and running light wires got switched. Or maybe the wire has been damaged along the way and only a thread or two are connected. (Test it where you jumped it, if it reads higher there then it's somewhere between that point and your tail lights, if its the same check things going forward. The wire should be pretty well protected though, but things happen. )Only thing else I can think of would be some sort of mixed up between 6v and 12v, but I'm not sure what in the tail lights could be effected by that. Truck still a 6v system or was it converted to 12v?

6v system
 

The system is 6volts with positive ground system. the lights seem to ground at the tail lamp on the left where it mounts to the body. I cleaned all contacts and applied dielectric grease at the tail lights and all the battery connections. The brake lights improved, but are still a bit dim, especially when the headlights are turned on. I now suspect it is not wired correctly. The engine cranks slowly, but I do get 6 volts from the battery. Is this normal for a 6v system?