No lights, and magic smoke appears

[slantflat]

Hi everyone.

Went to move my M35 this weekend and found I had no lights. No headlights, no turn signals, nothing. Jumped out to verify nothing worked and when I got back to the cab there was smoke coming from under the dash. I turned the light switch off real quick and the smoke stopped. I'm not good at spark chasing so here's a question.

Is the Deuce light switch prone to going bad? I've had wiring problems with the truck in the past and my first thought was the wiring behind the dash is brittle and cracked and shorted against something. Overthinking set in quick and that gave me the thought of a bad master switch. I was thankful the smoke wasn't accompanied by flames. If one has smoking wires, is it a thorough pain in the gluteus to wring out and fix? I've got the TMs and will look it up, just thought someone had some experience they'd like to share. I know there isn't a lot of room back there to work.

This will have to be a personal journey since with no lights I can't drive it up to have it worked on for me. Wish me luck.

Thanks everyone.

 

[Mullaney]

Hi everyone.

Went to move my M35 this weekend and found I had no lights. No headlights, no turn signals, nothing. Jumped out to verify nothing worked and when I got back to the cab there was smoke coming from under the dash. I turned the light switch off real quick and the smoke stopped. I'm not good at spark chasing so here's a question.

Is the Deuce light switch prone to going bad? I've had wiring problems with the truck in the past and my first thought was the wiring behind the dash is brittle and cracked and shorted against something. Overthinking set in quick and that gave me the thought of a bad master switch. I was thankful the smoke wasn't accompanied by flames. If one has smoking wires, is it a thorough pain in the gluteus to wring out and fix? I've got the TMs and will look it up, just thought someone had some experience they'd like to share. I know there isn't a lot of room back there to work.

This will have to be a personal journey since with no lights I can't drive it up to have it worked on for me. Wish me luck.

Thanks everyone.

.
Well, since the magic smoke came out - I suggest hand chasing the wiring. Brittle could be good enough to get home but brittle might just be bare wire depending on how much smoke got out. Some of these light switches are 20 or 30 or even 40 years old and still going strong. When one goes out though it can be over...

The good news is that there isn't a lot in the way under the dash. Of course laying on your back under the steering wheel is a pain. Might even be worth removing the seat to give you enough room to work.

 

[NDT]

The 3 lever switch has a 15 amp self resetting circuit breaker inside. All lighting circuits are protected by this breaker.

 

[G744]

Above is true UNLESS someone monkeyed with the wiring, usually caused by not understanding how blackout circuits are integrated into the system.

G744

 

[slantflat]

Thanks guys. I'll have a chance to look at it this weekend. How long does it take for the breaker to trip? I was away from the cab for probably 20 seconds and when I got back there was quite a bit of smoke. Last time I drove the truck everything was fine. Hm, it must be an airplane, broke while sitting.