Headlights go out while on high beam

[Superspark]

Hello all, I have an issue where my headlights work fine as do all of my lights while on low beam. I switch to high beam and within about a minute my headlights go out. They come back on as soon as I switch back to low beam. I replaced the floor mount dimmer switch and when tested the high beams stayed on for approximately 5 minutes and then went out. I am driving a 1972 Bronco, 302, 3 speed. The vehicle is virtually stock with zero upgrades or customizing of the electrical system. Any input would be greatly appreciated.

 

[Wrightracing]

I had that Problem and it was the Dash light switch was over heating and shutting down. Feel the dash switch to see if it feels warm. It's worth a check.

David

 

[Slowleak]

The headlight switch has a thermal breaker in it. If your high beams are pulling too much power it will heat up and trip…

 

[Superspark]

Ok I will check that tonight. I did replace the headlight switch probably 20 years ago....may be time for a new one. I've owned the Bronco 33 years... I appreciate the input and will keep you posted.

 

[Jdgephar]

You can also buy a relay kit to bypass the high power going through the headlight switch. It's a worthwhile upgrade.

 

[catfan]

Bad dimmer switch will do it too.

 

[okie4570]

Bad dimmer switch will do it too.

x2, every headlight related issue I've ever had has been from a bad dimmer switch. Both of my 58yo 66' still have the original headlight switches, I've replaced the dimmer switch 2x in one and once in the other.

 

[Wild horse 75]

Modern halogen headlights draw more amperage than these old switches can handle. You can buy relay kits to ensure you get maximum amperage to your lights so they will stay on and be brighter.

 

[BGBronco]

I did the HD harness. Definitely, a good upgrade, especially if you still have the original harness.

 

[DirtDonk]

What they all said. If it’s your thermal breaker, switch inside the headlight switch, you might even be able to feel the heat just by putting your hand on the dashboard. That’s what happened when mine started doing that.
I did actually have higher power high beams, but it started doing it on low beam, so I knew something was up.
I ended up creating my own relay system because I had seen that on some modern cars back in the 80s.
Fixed my problem and I’m still running the original headlight switch. Well, now that I think about it, I think it was the second switch that failed. Not the original.
I have also had to replace floor dimmer switches multiple times.
But they never acted like this. Turning off and on was always the circuit breaker in the switch for me.
When it was the floor switch, you could often get it to temporarily work by flipping it a few times. That’s when you know they’re on the way out.
They do take a beating down there on the floor. But since you have already replaced yours, and any replacement headlight switch will likely do the same thing down the road, you should consider the relay harness.

 

[DirtDonk]

I should add that the relay harness does not do any permanent modifications to your stock wiring. You can return it back to stock anytime you want.

 

[DirtDonk]

Oh, and another thing you can do right now, as a test, is disconnect one headlight.
See if that prolongs the on time, versus the off time.