The Stovebolt Site Forums The Shop Area The Electrical Bay Headlight switch maybe?

A problem I encountered driving home late one evening in my 1959 GMC.

It was dark and I had the headlights on and then I left the main road and headed down a secondary road. I decided to light up the world and turned the headlights to bright. Well after about 30 seconds everything went dark, and I had no lights. I managed to pull over, and I turned the lights on and started out again on dim, and the lights did stop momentarily but only a couple of times. I drove the rest of the way home with the lights on dim, and just before I pulled into the driveway I tried the bright lights again, and same thing, everything went dark.

The truck had just come out of the shop from a frame off restoration. The truck has the original wire harness, but has a new reproduction headlight switch. Could the switch be overheating on bright?

Any suggestions?

Sounds like the dimmer switch...

yep, i agree, sounds like a ground at the dimmer switch.... wire grounded to the chassis etc...dimmer switch gets my vote too.....

Do you have a fuse on the pull switch for the headlights? If it is fused, and you loose power to the headlights due to a short (ground), the fuse should burn, and the lights will not recover. If there is some kind of thermal fuse, then recovery may be possible, but I've never seen a thermal fuse used in a vehicle circuit.

Consequently, something is intermittently interrupting the power to the headlights, and it sounds like you are getting a intermittent ground or a loose connection. Loose connections can overheat and intermittently interrupt power (and also cause fires due to high resistance at the loose connection).

The dimmer switch could easily be the culprit--again due to a loose connection (with the attendant overheating), a false ground (also a potential source of extreme heat), or a ground in the dash indicator for the high beam circuit.

The headlight switch itself can have worn contacts that fail under the additional amperage of the high beam circuit.

Go find the problem and fix the offending rascally part or connection.

Glenn may be right. We had an aftermarket headlight switch in our '42 1/2 ton which had been converted to 12 volt. The switch has a thermal circuit breaker that had dirty contacts which under a load would heat up. After it got hot, we had the same symptoms that Northerngmc has. We got a new switch but learned all we needed to do was get an inexpensive replacemnt circuit breaker.

I had the same problem after installing a reproduction headlight switch. I found the problem to be the thermal contacts on the headlight switch. I just re-arched the contacts to what seemed a more appropriate angle. My experience seems to be the same as presented in some of the previous posts.

Sounds to me like your headlight fuse, which is a little "metal box" in your fuse panel and acts like a circuit breaker, is shutting off your lights when you put on the highbeams. It took a minute before your lights came back on, right? That's when it kicks back on, after cooling off.

Like everyone is saying, something is shorting out, causing the "shut-off" to kick in. Is it just possible you need a higher amp headlight fuse in your panel? Or, it may also be possible that your headlight fuse itself is faulty ... aside from the above solutions, this may be something else to consider.

Like others, my vote is with the dimmer switch. Take it apart if you can. You will probably find the high beam contact is burned, likely due to the sliding/rotating contact not making full contact with the high beam connection. Sometimes aftermarket stuff isn't exactly built with high quality.

Have you solved this one?

You clearly have a problem somewhere. You said it was fresh from the shop with a frame-off restoration. Is it truly restored with a full original type harness, switches and lights?

Your symptoms sound like what often happens if you put halogen headlights with a standard switch. The lights require more power than stock, and are too much for the switch to carry.

Is the headlight switch a modern type? They have breakers built in to them in case of a short in a light or wire. You may need to add a relay to the high beam side as the switch may not be able to handle the load. Try to find a replacement switch from a USA made vender. Halogen bulbs pull a lot of current if thats what you are using. Joe

If the 59 is like the AD series, there is a circuit breaker in the headlight switch that protects all the circuits coming from the headlight switch. If your dimmer switch is shorting, this could produce the exact symptoms that you describe. The fuses on the firewall protect the external wiring, like the headlights and tailights. If they blow, they stay that way. A fuse cannot recover.