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Joestein · 03-13-2021, 02:58 PM

I have one fuse that controls digital odometer and also the side marker and running lights. Fuse keeps blowing as soon as I turn in the lights? Will work fine and stay good while just driving and odometer and speedometer work, but as soon as I hit light switch it blows the fuse. Any ideas where to look or similar experiences? Thanks

Skip426 · 03-13-2021, 05:54 PM

Wire in a 12 volt test light in place of the fuse , then turn on the lights ,the test light will be lit up as you look for the short .
The trouble spot may not be lit , or be dimer than other lights , that's the first place to look for the short.

Jim_HiTek · 03-13-2021, 05:54 PM

Dunno about those exact symptoms but you can make your own test aid by buying a modern 12 volt dual filament automotive bulb, they're kinda expensive at retail these days so I look for them at yard sales. Straighten out the wires, twist the filament wires together so that the filaments are in parallel and then crimp on spade terminals.

With that test aid inserted into a spade type fuse socket, you can now explore with a DVM and where the voltage is lowest is where the short is likely to be. What happens is that the filaments glow dim under normal circumstances and when whatever happens to cause a short occurs, the filaments glow bright, giving a telltale indication of where to look or what to work on.

Here's the style bulb that works best in this modification, and it works best when the target circuit fuse is under 10 amps, but it'll often show you something even in a 20 amp circuit.

https://www.amazon.com/Double-Filame...682960&sr=8-79

Dutch Star Don · 03-13-2021, 08:39 PM

The poor man's way.....remove all running lights or at least start with one that you think is the offender and reinstall them one at a time, until the fuse blows. You've got one shorting out, most likely a rusted out socket.

Joestein · 03-16-2021, 12:53 PM

Tried removing all running lights bulbs. Tail light, license plate, side light, all top lights. Still blows fuse instantly. Checking all wire connections to see if they are good. Can't even think where to start if it's a scrapped wire. Any ideas are helpful.

SKP Kirk · 03-16-2021, 03:04 PM

If it does turn out to be a wire that has lost it's insulation, about all that I know of to do is to trace wires back from each light toward the light switch.

Jim_HiTek · 03-16-2021, 03:29 PM

Quote:

Originally Posted by Joestein

Tried removing all running lights bulbs. Tail light, license plate, side light, all top lights. Still blows fuse instantly. Checking all wire connections to see if they are good. Can't even think where to start if it's a scrapped wire. Any ideas are helpful.

Using the DIY telltale device I mentioned above or a similar device as mentioned by Skip426, you can often tell where the wire short is because the bulbs before the short still glow and those after don't.

Joestein · 03-16-2021, 03:42 PM

I did get lucky and finally find it. After searching high and low and checking all lights and wiring to fixtures, made sure all were heat shrink Ed and protected. Made sure none had screws through wire to cause a short. Found the problem inside of the front fog light, turn signal socket. It has 3 wires going into it and wires are kept apart by a little rubber gasket. The wires inside had slid over and we're touching causing the rapid fuse pop. Once I was able to terminate again everything worked. Sealed all lights back up and made sure everything was good. It only took a few days of searching so could have been better, but could have been worse.