I have a 65 F250 the headlights work fine until you put on the brights. After a short time the lights will go completely off than return on. This repeats. Turn the brights off and no problems.

I understand there is some kind of built in circuit breaker in the switch. Is this a common problem with the switch or am I looking at other problems causing a trip.

 

If you're running halogens they may be drawing too many amps for the headlight switch. You can either wire in a relay to power the headlights or replace the switch ,, the new switch will probably be able to handle the halogens. Personally I always rewire them with a relay and a 30 amp fuse.

 

Thanks but the headlight system appears original that's why I need the brights can't see half the time with low beams.

 

Sounds to me it is either a bad connection at the dimmer switch or the dimmer switch is bad
Good Luck Sonny

 

You describe a common problem with all old Fords of this vintage, whether it be F100, Mustang, Falcon, or Galaxie. There is a circuit breaker built into the headlight switch which wears out, exacerbated by old tired wiring and possibly a weak ground. High draw headlights will make the problem worse, but even stock headlights can have the problem. It shows up just as you describe, with the CB tripping after the high beams are selected, causing a total loss of headlights, then resetting after a moment after you have hit the dimmer switch back to low beams. Back in '66, I tried to fit some aircraft landing lights into the high beam bulb position on my '65 Galaxie. Though the switch and wiring and grounds were all relatively new, the lights pulled too many amps and tripped the CB in the switch. I would have needed to install a relay or remove the lights. Since I was a poor college kid, I removed the lights. Because of the age of your truck now, I would start with replacing the headlight switch, and give the wiring and grounds a good hard look and replace as necessary. I don't know if there are higher capacity headlight switches available for F100s, but I believe there are for vintage Mustangs. Hopefully someone on the forum will know. Good luck.

 

Next time this occurs, click on the dimmer switch on the floor, see if the headlamps come back on.

 

I'm sorry, yes the lights go back on after shutting down the high beams. I have never waited out to see if the lights go back on without turning off the brights as I am typically driving at the time. Also have never had the failure with just low beams. As far as I can tell it's a stock set-up.

 

So, that switch on the floor that you use for the high beams - that dimmer switch itself is one of the suspects at this point. Often people whose high beams don't work or only work for a moment - they change out that floor switch and all is well. But, with a multi-meter you also might be able to test and tell if the switch is bad, too. Might not be the end-all-be-all test but it might show if it is in fact faulty.

Chad