Mystery fried wire(s)

Fantastic11, thanks a million for the photos!

 

Not a problem. Happy to help!

 

When I cut the damaged wire, but before adding a jumper wire, I thought the fuel gauge would appear off after I reconnected the battery but it still showed the tank being full (which is accurate). On most vehicles, when the key is off, the fuel gauge appears off, then shows the fuel level once the key is in the ignition position. Is the 1st gen Tacoma different in always showing the tank level, even when the truck is off, or is this another anomaly of my truck perhaps related to the negative fried sender wire?

Below is a photo of my truck wiring in the same vicinity as Fantastic11's photo. I have melt as far as I can see up the wire. There is no junction box between the under-seat J/B and where it appears the burned wire would join the ground wire at the bolt (that wire shows no damage) at the upper left of the photo so I'm still wondering where those relays are located (if I'm reading the wiring diagram correctly). I guess I'll just have to drive the truck around to see if the fuel gauge still works

Does anyone else think that harness binder "ring" is squeezing the harness too tight? I'm going to change that out.

I did get my kill switch installed successfully so there's one thing to celebrate.

 

I've been sitting on the sideline watching this.. Way back in the day... I installed a kill switch, tapped into the lines headed to the fuel pump under the seat at this harness. I was young, didn't know a whole lot about wiring in general at that point. I used a larger gauge wire to add a switch hidden away somewhere else. BIG mistake. Eventually I fried that whole harness. The hard lesson I learned was: gauge matters. I hope you matched the gauge when you installed your kill switch (if not, you should seriously consider redoing it).

I was going to mention incorrectly gauged wire on that or a related circuit earlier, but because I didn't have a direct link between the fuel pump and the sending unit ground, it didn't seem to add up. I'd still consider following that circuit end to end and finding out if someone before you did something funky.

 

Interesting. I’ve read that it’s OK to go bigger, never smaller. The amperage on the load wouldn’t change so how could your bigger wire have caused an issue and how were the other circuits in the harness affected? I did match the gauge in my install but I’m definitely at the stage where I might not know any better, so I’d appreciate understanding the physics.

 

Your correct bigger is fine !!

I always use larger gauge wire for a few years (mid seventies) with no melt downs .

After all were talking the flow (bumping) of electrons Which gets real confusing . You want to know more send me a message.

Then any increasing the gauge of battery cables would cause a meltdown as well!