Fried wire from alternator

[stockmax]

Alright, it’s been a while since I’ve asked anything of the collective ih8mud minds, but I’m trying to figure out why this bit of wire fried itself on my 40. It’s coming from the alternator and is a ground which is really strange.

Anyone ever seen something similar and if so what was the issue?

My temporary fix might be to upsize the wire but I don’t want to do that and not fix the fundamental issue risking a more catastrophic failure.

Thoughts?

 

[edwjmcgrath]

If your ground connections at the battery, frame, and engine are not solid, then the electrons need to go somewhere and they often will go backwards up any wire that is connected to the ground at the battery in search of a better path. That could cause what you are seeing. I would start there.

 

[thebigredrocker]

@Coolerman @bj40green @MrMoMo

 

[stockmax]

If your ground connections at the battery, frame, and engine are not solid, then the electrons need to go somewhere and they often will go backwards up any wire that is connected to the ground at the battery in search of a better path. That could cause what you are seeing. I would start there.

Thanks!

I’m going to give that a shot and see how it does.

 

[hobbes]

Yeah. Check your ground to frame, your starter to frame, and your alternator to engine block path. I had an extra ground wire laying around and ran that alternator frame to engine head. Good luck.

 

[thebigredrocker]

here's a similar situation

Toasted ground

Evening folks, Anybody know if this toasted ground is from the starter? It's a 77. Noticed smoke when she was having trouble turning over. Thanks

forum.ih8mud.com

That pic shows a classic problem with the FJ40 wiring system. If the starter or the alternator does not have a good solid ground, they will attempt to pull current through any ground that is good in order to do their job. Usually through the alternator, regulator and ignition grounds. Since these are smaller 14 or 16ga wires they WILL melt.

In addition to the starter ground to frame, and the engine block to frame, make sure the alternator is well grounded to its mating bracket, and the engine. You can use a bonding jumper of say 10 ga between the body of the alternator and the engine block if you don't want to dismount and clean the alternator to mounting brackets to engine. Just I would add that bonding jumper anyway in addition to properly grounding the alternator through its mounting bracket.

You also need the proper 3 pin latching connector for the alternator to attach ground wire and the white/green wire. I sell this connector and new terminals cheap. Part #FLF3P6.3W $2.55 + $3.00 shipping. Send me a PM to order. I also sell the White/Black wire in 14, 16 and 18ga sizes by the foot, just tell me what ga and how many feet you need.

You are going to have to un-tape that harness and see if that melting goes deep into the harness. It may have melted other wires together which will cause no end to your weird problems! If it does appear to have gone deep, and damaged other wires, the proper way to fix it will require pulling the harness off the truck, completely un-taping it, replacing the damaged wires and taping it back up. I also sell the correct non-adhesive harness tape for that job. (I also stock all the proper color striped wires for your truck)

Good luck!

 

[stockmax]

here's a similar situation

Toasted ground

Evening folks, Anybody know if this toasted ground is from the starter? It's a 77. Noticed smoke when she was having trouble turning over. Thanks

forum.ih8mud.com

Sanded down the ground from battery and ignition coil to body. Replaced the melted ground from the alternator and the neighboring wires were all good so no need to replace everything.

My one question is this wire coming off the ignition coil that doesn’t seem to have a home. Anyone k ow what it’s for? Is it another ground?

 

[edwjmcgrath]

Some ignition systems have a coil that normally runs at around 6v but when the starter is engaged, runs at a full 12v so that you have a brief hot spark. That may be the wire that feeds 12v from the starter when it’s cranking. There are a bunch of reasons why you may not need it. If you start fine, don’t worry about it. Or sometimes, people use the coil positive as a place toi get 12v for another use. It may be that but no longer used.

 

[stockmax]

Thanks again to everyone for the wealth of information. Really appreciate the help!

 

[Dizzy]

That black wire by the coil is the 'noise filter capacitor wire.' It can help with grounding for AM radio to keep the motor's ignition system noise out of the radio signal. The black/white wire from the coil is the 'starter bypass wire,' getting full voltage to the coil during starter cranking.

It kinda looks like you have both an igniter and a capacitor. My rig came that way, where a previous owner changed it back to old-school points, but they got rid of the igniter - luckily I got one from another 2F, so I have less wear on the points. I'd be curious about how the ignition system is wired.

Check the grounding on the voltage regulator on the driver's side firewall in the engine compartment. There should be a ground from the alternator to this and it kinda looks like it got hot on the alternator side. I looked at this post a few times now, and I'm pretty clueless as to what could be the issues origin.