Pulled alternator found broken melted wire

[sdjaytee]

Hi all

I had my alternator out of my 81 SC engine and found this situation, one of the three wires connected to that bottom right post is broken and the insulation melted. No idea when this happened but I have been driving the car around plenty without any noticeable issues. Which of the wires is the one broken/melted? How dangerous was or is driving with this wire not connected?

[thetorch]

Those brown wires are ground wires. Either the unfried grounds or the existence of a ground strap from the engine case to the air diverter bolt / alternator case is providing ground so it's still working.

Judging from the photo, your power (red, +) from the starter has a lot of bare cable exposed by the eye and it may have grounded to the ground wire and melted it. I would clean up the exposed red cable -- if it touches anything metal under there other than the stud it's on, bad things will happen.

It's a big problem waiting to happen. Shorten the lead and get some heat shrink on it. Wouldn't hurt to get terminal boot too.

[thetorch]

also clean up the cooked ground wire of course.

[DaytonaCoupe66]

If you've not had a failure yet the gods are smilin' upon you. My ground wire to the case also let go a few years back. Tach stopped working, then slowly other electrical functionalities started shutting down. I thought the alternator had died, but was happy to find that broken wire. Sometimes a simple fix does it!

[thetorch]

I should have mentioned: that red wire is always hot (key in, key out, engine on, engine off -- doesn't matter), so make sure you disconnect your battery anytime you go in there.

[sdjaytee]

Originally Posted by thetorch

I should have mentioned: that red wire is always hot (key in, key out, engine on, engine off -- doesn't matter), so make sure you disconnect your battery anytime you go in there.

Thanks for the info, def disconnected the battery before getting in there. I started peeling back the heat wrap and the cooked ground wire goes pretty far back, I’m guessing new engine harness?

[thetorch]

After reading innumerable threads on the alternator wire grounding, my understanding is that you can probably replace those 3 ground wires with a ground to the engine case where the grounding strap that attaches to the air diverter goes using a beefy (6 AWG) wire from the alternator to the case. I believe those 3 browns are grounded elsewhere on the engine or chassis, but serve no other purpose than to ground the alternator. Good to check the power cable's integrity in the harness.

Worth reading:
Alternator ground wire insulation melting


Alternator ground strap

[timmy2]

Those 3 ground wires are ground paths for the blower motor, and multiple CIS devices.
They are not grounded elsewhere.
The alternator is grounded to the case .

PM or email me if you decide you need a new harness.

[thetorch]

^^ Listen to Timmy2, he knows way more than me. Unless like me you don't have a blower motor or CIS.

[smadsen]

The alternator to case ground is always brittle, rotten, or disintegrated. I think constant heat soak after engine shut down combined with age. Either make a new one or I think our host carry's a p/n for a factory look.

Some of those other wires need splice repairs, shrink wrap and/or replacement. Good opportunity to clean cooling fins with compressed air.

[sdjaytee]

Originally Posted by thetorch

^^ Listen to Timmy2, he knows way more than me. Unless like me you don't have a blower motor or CIS.

Thanks all!

timmy2 a local shop is taking a look and if we need a new harness I’ll reach out. I do have cis but no blower motor.

[timmy2]

Originally Posted by sdjaytee

Thanks all!

timmy2 a local shop is taking a look and if we need a new harness I’ll reach out. I do have cis but no blower motor.

Sounds good. So many people have different mods they have done like backdating heat or running headers negating the need for a blower motor is why I always build to order.

[sdjaytee]

Update, the engine wiring harness was cooked all the way. Partial engine drop and lots of things removed to get to all the wiring. Harness was replaced the alternator was done and replaced. When the engine was partially down we found the air intake boot was severely cracked and broken around the back and replaced. I also opted to replace and do a few other things while it was down. When it rains it pours but the shop did an amazing job!