Black/Red Ignition Wire Burnt Up (1 Viewer)

[ryanwk628]

A few days ago I was drove my 11/69 FJ40 to lunch and when I got in it to go, smoke instantly started coming out from under the dash. I turned the ignition off, disconnected the battery and checked for fire before having AAA come pick me up and going back to work.

Today I dragged it out of the garage and started looking into what happened. It did not take long to realize the black and red wire from the ignition had burnt up and shed its coating almost back to the firewall.

Burnt up wire

Pulled out

The ignition wires looked twisted up and I assumed this one had broken its jacketing. I cut the burnt up section out and tried to make up a new piece of 14ga hoping that I could at least start it.

The head lights were not wired up when this happened so I completed that task today before trying to address this wire.

Fuse looked good. When I tried turning the ignition it clicked one time and quit. Ive rolled it back into the garage (parking only, not much room to work) and am reassessing.

I need some help. Does anyone know what I should be looking for? What would you do first?

Thanks a lot,
-Ryan

 

[thebigredrocker]

Dang it. I'm sure @Coolerman could rattle off exactly what to look for. From the schematic it appears the BR splices into the big WL. Perhaps post some photo's of the WL connection at the ammeter, alternator and fuse block. Did your WL suffer any damage? I've read that dirty connections can cause resistance issues.

Coolerman has mentioned the two WB ground wires that attach to the voltage regulator are super important as they ground the entire harness. You might clean those up while you're at it.

 

[jm599]

Did that year have a fusible link?

 

[White Stripe]

First I would check the fuses. Make sure the correct amp fuses are in each spot. Then I would print out a diagram of the wiring just like you have for us here but one you can write on and kind of mess up and throw away after. Then highlight all the wires related to the system and that are related to your bad wire. Take notes of what each wire does that are related. Then make notes where your going to check resistance and write what range the resistance readings should be. As you take readings write down on your diagram actual readings. Have u pulled your cluster out? Looks like your amp gauge wires are related to the system. Pull the cluster, unplug it, take the amp wires, disconnect them from the gauge and use a nut n bolt to screw them together to each other and put tape around temporarily. Then u have access behind the dash, and with then wires together u can start it and test it with the cluster out. Disconnect the battery b4 removing the gauge cluster or you'll get a firework show.

 

[ryanwk628]

First I would check the fuses. Make sure the correct amp fuses are in each spot. Then I would print out a diagram of the wiring just like you have for us here but one you can write on and kind of mess up and throw away after. Then highlight all the wires related to the system and that are related to your bad wire. Take notes of what each wire does that are related. Then make notes where your going to check resistance and write what range the resistance readings should be. As you take readings write down on your diagram actual readings. Have u pulled your cluster out? Looks like your amp gauge wires are related to the system. Pull the cluster, unplug it, take the amp wires, disconnect them from the gauge and use a nut n bolt to screw them together to each other and put tape around temporarily. Then u have access behind the dash, and with then wires together u can start it and test it with the cluster out. Disconnect the battery b4 removing the gauge cluster or you'll get a firework show.

Thank you for the heads up about the cluster. I have my battery out of the vehicle but will note that for future reference. Fuses look good. I have a couple 11X17s of the diagram Ive been referencing (you can see it in my second photo).

Tracing the wire out it goes to three fuses, then out to the lights with switches along the way, the horn relay and alternator. It had to flow a lot of current to cook up that fast so I am thinking it arc'ed a power wire or a relay somehow started sending juice up the wire. Could a lighting wire have touched off the ground and caused a huge draw?

 

[White Stripe]

Thank you for the heads up about the cluster. I have my battery out of the vehicle but will note that for future reference. Fuses look good. I have a couple 11X17s of the diagram Ive been referencing (you can see it in my second photo).

Tracing the wire out it goes to three fuses, then out to the lights with switches along the way, the horn relay and alternator. It had to flow a lot of current to cook up that fast so I am thinking it arc'ed a power wire or a relay somehow started sending juice up the wire. Could a lighting wire have touched off the ground and caused a huge draw?

Hook up your battery, and try to start it while grabbing the wire you replaced and see if it feels warm. If not then, try jumping/bypassing the ignition switch and see if it cranks. Make sure its in neutral. If it doesn't crank test for power through the switch.