Dimmer Switch Causing Headlights to Go Out

[Charlie7985]

For the second time in a year I have had my headlights start coming on and off suddenly while driving at night on my 79 C10. Eventually, they would stop working at all. Changing out the dimmer switch in the floorboard resolves the issue. The first one was a Duralast from AutoZone and the second was an AC Delco. Has anybody else had this problem? Does anybody know where to get a quality switch or if there is something else causing this?

 

[Ricko1966]

The headlights switch has a breaker in it. If the circuit is overloaded the breaker goes on and off until the problem is resolved or the breaker is so overheated it just won't reset. This is why GM headlights don't have a fuse its safer to have the lights go off and on than to just complete blackout all at once and no headlights again until you replace a fuse. I'd check all the headlight wires and headlight wire connections and grounds. Bad connections increase resistance. Increased resistance creates heat. Heat melts switches and heat sets off breakers. Have you added to or changed any of the headlights from factory?

 

[goldpack]

are you using the same old wiring harness? just wondering.

 

[rancher1913]

ive got the same issue, new dimmer but problem still hangs around. cleaned all the grounds. only does it on low beam, high beam works just fine. im thinking i got a bad new dimmer switch

 

[Ricko1966]

@rancher1913 and @Charlie7985 It's easy to run a volt drop test on the switch. I doubt the switch is your problem. With the headlights on in low position hook one lead of a meter to the power in wire, hook the other lead to the power out wire. Look at your meter,does it show less than .5 volts? If so the switch is good,if it shows more, the switch or the connection to the switch is bad. @Charlie7985 test yours in high position and low position.

 

[NLD79K10]

I run a separate wiring harness that uses a pair of 30A relays to power the headlights (straight from the battery) and switch between dipped and main beams so the full current doesn't run through the headlight and dimmer switches and chances of either switch burning out is a lot lower as they only run the current required to flip the relays. I built it so that each headlight is on its own fuse, that way if I do have a short in either headlight, I still have the other headlight working.

 

[75gmck25]

My dimmer swirch is still original, and sometimes it’s flaky and just shuts down the lights when going from low to high beam. My fix is to just hit it 3-4 times and it finally switches correctly. Not the most elegant solution, but I don’t use high beams that often, so it works for me.

I also have one of the LMC headlight relay kits, so full headlight amperage does not go through the dimmer and headlight switch. I did that primarily to ensure I get full voltage through old wiring.

 

[Charlie7985]

I did a complete rewire of the engine bay six years ago from scratch to match the factory wiring harness because I had such a rats nest. I did use halogen bulbs, but I haven't had a problem with this until recently. I am ordering one of the headlight relay kits from LMC Truck to install with another new dimmer switch.

 

[Grit dog]

I did a complete rewire of the engine bay six years ago from scratch to match the factory wiring harness because I had such a rats nest. I did use halogen bulbs, but I haven't had a problem with this until recently. I am ordering one of the headlight relay kits from LMC Truck to install with another new dimmer switch.

If they’re still available, look for the Toyota Landcruiser headlight deal. It’s also posted here somewhere. The relay kit is top notch and the whole thing with new round headlights is about the same $ as a relay kit.
Regarding the dimmer issue. Bypass it and see if the problem still exists. Easy diagnostic procedure.