The Stovebolt Site Forums The Shop Area The Electrical Bay 1951 3100 Headlight issue 12V

Had headlight failure and put in 1 new headlight H6204 from Sylvania Silverrstar. The headlights only work on High Beam. Why? Could it be the dimmer switch? All other lights function correctly. Thank You Bill

The dimmer switch is a good candidate. My 1951's dimmer switch that came with it, and another that I got only work intermittently. I found a NOS one that checks out fine with a multimeter (low resistance across the terminals when switched) that will be installed in the spring. They live down where they get blasted with road gunk.

Assuming the other headlight worked on both high and low beam before installing the new H6204 the problem is with the dimmer switch or the low beam wire from the dimmer switch to the terminal board near the front of the drivers side inner fender sheet metal.

Quick test: Aim your truck at a nearby wall. With the headlights off, use a jumper wire between the hot wire on the brake light switch and each terminal on the dimmer switch. One terminal (the headlight switch voltage feed) should do nothing, one should light the high beams and one should light the low beams.

If both side high and low beams come on, the dimmer switch is bad.

If high and low beams work on the drivers side, but not on the passengers side either the passengers side headlamp is bad or the wiring between the drivers side terminal board and the passengers side headlamp socket is bad.

If high and low beams work on the passengers side, but not on the drivers side either the drivers side headlamp is bad or the wiring between the drivers side terminal board and the drivers side headlamp socket is bad.

I had this problem on my truck.

It turned out that the previous owner, who was dyslexic, mixed up the hot wire and the high beam wire at the dimmer switch.

I I turned on the headlights, power went directly to high beam terminal. When I pressed the floor button, it turned off the lights altogether.

There are three terminals on the dimmer switch. I don't remember exactly which is which but if the hi beam indicator comes on, you'll know which side is hi beam.

If what Bill said about neither high or low beams working on one side is happening, I would also check the ground wire to the inner fender. A complete circuit is needed for the lights to work.

The attached pic will help with correct wiring of the dimmer switch. Notice the "BAT" marking? That terminal is where the hot wire goes. The other two don't matter (one goes to low beam and the other to high beam.)

Thanks Kvin. I deleted the sentence with my ill-remembered info about which terminal is hot