Headlight flash

[nadams]

When I turn the brights on in the 68 f250 the lights will flash on and off about 20 second on each cycle. Turn off the brights and it stops. Has anyone had this happen before?

[Joshpow]

Probably a bad switch or wire. Being the electrical is so old, the switch or wire may be overheating while on the higher amperage high beams.

[seattle67]

It could be a few things Nathan. If they are doing it one at a time, I would check the connection on the back of the head lamps first. If they are both flashing off and on at the same time, I would look at the connection at the dimmer switch or the dimmer switch itself. Then the connection at the light switch and then the light switch itself. Thats a start anyway....

This is why I'm going to get one of Pauls headlight wiring harnesses. Low voltage at relatively high amperage, going through little wires, old switches and dirty connections = out go the lights.

[fordman]

its a cop car. no its probably a bad switch.

[FORDification]

The light switch has a circuit breaker in it....that circuit breaker is being tripped. You just gotta find out why.

Did this just start happening? Did you do any work to the electrical system prior to it doing this?

[nadams]

This is a previous problem. This is the f250 I just bought. The PO told me about the problem. He seemed to think that the highbeams worked fine until they warmed up. I will change the dimmer switch tomorrow. Luckily I bought one from fordman last month,

[390Nut]

Agree with what Keith said. If it's after it warms up a little (wiring/switches, actually heating up from usage) it's likely the headlight switch itself being tripped internally. Check your grounds and make sure where they connect is clean, check all the connections in the wiring, check the back of the headlamps for loose terminals that could cause a short.

[seattle67]

I forgot all about the circuit breaker in the switch, thanks for the reminder guys!

[4th effie n counting]

I had a similar problem in a mustang years ago. In my case after about 5 minutes on bright, lights went out altogether. I discovered this about 1am on a curvy mountain road! luckily it was a full moon, after about 10 minutes i drove home on dims I just never used brights again