Blowing tail light fuse, possibly short in headlight switch? (1 Viewer)

[tarheel40]

I’ve had my 76 FJ40 for about 6 months, no electrical issues, and as I’m driving down the road last Saturday night my dash lights suddenly go out (after hitting a medium bump). After getting back home I realized it wasn’t just the dash lights but the whole circuit - parking lights, tail lights, etc. The 15 amp fuse at the top of my fuse box was blown, I replaced it and was immediately back in business. Figured the fuse had gone bad, no big deal.

Drove the 40 some the next day (headlights not on) and then checked the lights that night just to make sure everything was working - fuse blew as soon as I pulled the headlight knob out and lost the whole circuit again. I took all the bulbs out of every light on that circuit and the fuse blew again as soon as I pulled the knob out (even before headlights came on). Checked all wiring, harnesses, etc and no obvious exposed wire, shorts, etc. I took the headlight switch partially out, unplugged the harness, adjusted the dimmer a few times and then viola - everything worked again. My dimmer isn’t dimming for what it’s worth, only an on/off switch and I’ve haven’t gone to LED dash bulbs (yet!).

I checked the lights almost every night this week and everything worked fine, even after a short test drive. Took it out for a spin tonight and after about 10 minutes the same fuse blew. It seems like I’ve got an issue in my switch the best I can tell? Does this sound familiar to anyone? I’ve got the dash out and the headlight switch completely out, still don’t see any obvious shorts with the wiring except for two exposed wires coming from the middle of the dash that I’ve now covered up (don’t think they’re even on that circuit?). Is there anything I can do to take this switch apart and diagnose further (not an electrical guru)? It was a bit dirty around the connectors so got that cleaned up. Hate to just buy a new switch since I’m not positive that’s the problem and honestly not even sure if they’re available. Here are a few pics. Any and all help is appreciated, this is driving me crazy!

 

[1911]

Another common cause for that is previous owner added trailer lighting, you might check for that also.
Good luck in any event.

 

[Godwin]

I had something similar happen with the fuse for running lights blowing when the headlight switch was pulled. In my case it seemed to be related to the rheostat and only when the dash lights were cranked to maximum. At lower levels for the dash lights there was no problem but once the rheostat was turned up to full the fuse would blow. I've never tried to fix it, I just adjust and live with it.

 

[tarheel40]

Another common cause for that is previous owner added trailer lighting, you might check for that also.
Good luck in any event.

Thanks for the suggestion. I had seen seen that mentioned in several threads and checked, don’t see any signs of additional wiring added for trailer lights. I also unplugged the rear light harness near the rear axle and was still blowing that fuse, so I eliminated everything in the rear of the truck.

It’s either parking lights, gauge lights, the dash pad light or the switch mechanism. Being that the short seems intermittent and my dim function isn’t properly working I really think it’s in the switch.

 

[tarheel40]

I had something similar happen with the fuse for running lights blowing when the headlight switch was pulled. In my case it seemed to be related to the rheostat and only when the dash lights were cranked to maximum. At lower levels for the dash lights there was no problem but once the rheostat was turned up to full the fuse would blow. I've never tried to fix it, I just adjust and live with it.

This sounds very similar to what I’ve got going on. My dim function isn’t working, if I crank the rheostat all the up it just turns my gauge and dash pad lights on. It’s basically an on/off switch which I’ve seen can happen when the dimmer is “tired”. Earlier in the week if just left it full open and gauge/dash lights on everything was working so I was planning to live with it too, and just never try to dim. I was pretty disappointed last night when the fuse blew with the rheostat in that position - maybe a bump on the road caused that position to temporarily change and that’s when it blew.

I have no idea how to refurbish the dimmer function or what could be causing the short - @ToyotaMatt any ideas? Or do you have a switch I can buy to see if that solves my problem?

 

[ToyotaMatt]

This sounds very similar to what I’ve got going on. My dim function isn’t working, if I crank the rheostat all the up it just turns my gauge and dash pad lights on. It’s basically an on/off switch which I’ve seen can happen when the dimmer is “tired”. Earlier in the week if just left it full open and gauge/dash lights on everything was working so I was planning to live with it too, and just never try to dim. I was pretty disappointed last night when the fuse blew with the rheostat in that position - maybe a bump on the road caused that position to temporarily change and that’s when it blew.

I have no idea how to refurbish the dimmer function or what could be causing the short - @ToyotaMatt any ideas? Or do you have a switch I can buy to see if that solves my problem?

YES i can help here i have Fully Restored Headlight dimmer switches ready for immediate shipping , no delay or wait period ,....

will need to find out if you have a 60010 or 60011 ?