Head Light Issue
 

Whether or not you did something "wrong" is hard to say. But it seems safe to say something you did caused an undesirable malfunction. The first thing to try is to go back and retrace your steps, undo whatever you did until the headlights work right again, and then rethink the brake lights. You may have a crossed wire somewhere between the brake and tail connections, backfeeding through the headlight circuit. While it could be totally unrelated, chances are if they worked before, and don't work now, the problem lies in your 'fix.'

You haven't given us much information. I'm assuming that this is a '51 F3? Maybe an old wire got broken or a connector came loose while you were working on it. I would start at the dimmer switch. Hopefully you have a multimeter or at least a 6V test light.

Sergio

as already suggested, try looking for voltage at the dimmer switch. If you have high beams you should have power to the one side of the switch. Try low beam and look for power going out. Could be switch is defective.

The headlights get power from ignition on to the main light switch. Check wiring at the dimmer switch .

Quick stupid question.
So I’ve gone back checked all my connections.
Everything seems ok. I’ve gone ahead and changed to dimmer switch on the floor and I’ve changed the headlight switch

still the same issue. All the lights work. My parking lights. My brake lights. And my high beams. But not my normal headlights.

I’ve recently changed the bulbs. Is it possible the auto parts store sold me 12 v bulbs. Would the high beams still work if they were 12V on 6 V system ??

It's possible they sold you headlights for a quad-light (two low, two high) system, but they would only have two prongs on their backs vs. the three you need.

A 12V bulb on 6V will burn, but very dim.

Did you check your headlamp plug to see if you have power to the plug/bulb? If you do, then it's a bulb issue (if we're ruling out ground since half of the bulb does work) and you can double check the bulb for continuity across the prongs to be sure. If not, then trace the wire back to where you find power. Electrical problems are frustrating head scratchers, but are usually simple once you find the cause.