Technical Short in floor dimmer?

Is it possible to have a short in floor dimmer switch?

every so often when I switch between high beams and low beams the headlight fuse blows.

I’ve added relays so the only current traveling through the switches is to trigger the relays. I’ve checked the wiring and can’t find any chafing,
the dimmer switch seems low quality.

is it possible for the switch to short internally?

I’ll pickup a replacement next time I’m in town, hopefully that solves the problem.

 

Electrical issues ehh? How revolting. Hehe.

 

Yes, it's entirely possible. Had it happen on my '55 Ford years ago. Replacing the dimmer switch fixed it.

 

It is likely that the switch is shorting to ground internally. If you remove the switch from it's mounting, (isolating it from the ground circuit), and try it again. If the fuse does not blow, change the switch. They are the first thing to check (after fuses) when you get headlight troubles.

 

mine was body to frame grounds, ran larger gauge wire from headlights to body and even larger gauge from frame to body. 12 years ago and still working fine.

 

Regardless of age, or care given, the foot switch gets more abuse than most

 

The problem I had was someone put that shiny silver sound deadening in my truck, and when they bolted down the dimmer switch it shorted out on the sound deadening. I made a gasket to fit under the dimmer switch, and problem solved.

 

If the lights are on relay's I don't see how the dimmer switch could blow the headlamp fuse. Where are you getting power for the control circuits on the relays? Are they on a seperate circuit or are you using the headlamp circuit as the control for the relays? It all depends on how you wired it as to what the problem is.

 

Next time it blows the fuse you can test it with a meter (it's basically shorted to ground at that point). I've been buying new aftermarket ones from the 90s (Made in USA) for replacement.

 

Don’t replace it with a Lucas….

 

They're down on the floor under the carpet, where moisture can collect. So yes, they can go bad.

 

I'd go with shorting internally.
My daily driver at the moment is proof that floor mount dimmer switches corrode internally.

 

Thanks for the great suggestions.

I unbolted it from the floor and it doesn’t seem to blow the fuse when not attached and to the car. This must mean that it is shorting through the body of the switch.

The car has a rebel wiring harness, but I wired it so that the headlight circuit in the harness only triggers the relays. There are now two relays, one for high and one for low beam next to the battery, with a separate fuse. This is a trick I learned on foxbody mustangs to get brighter headlights.

I’ve got a replacement switch in the way to try today.

 

Weird,
If you hold the button just right you get continuity between the base and the terminals.

new switch is installed. Standard Motor Products was available immediately, but I’ll look for a nos switch and swap that in when I find one.

 

Glad to hear the issue has been found and appreciate you shared the result.