Cringe-worthy wiring (Alternator Help) (1 Viewer)

[KingAir Driver]

Ok... So the PO stated when I bought the vehicle that he had replaced the alternator with a high output single wire AC Delco (unknown amps) internal regulator to run the snow plow he had installed and that the ammeter was not hooked up. He had also replaced the points with electronic. So as I was cleaning up the 5th grader wiring connections and I found a few wires that had burned for unknown reasons. hmmm... The PO installed a 10 gauge wire going from the Alt into the cab, then another one came out going to the +Batt with a 16 gauge fusible link. ????? This got me concerned as to why the alt was not going to the +Batt and then onward to the ignition and so forth.

So I start taking apart the wire loom where it looks "un-original" and behold the White-Light Blue main wire is totally fried, all the way to the cluster. Both 10 gauge wires were running to the the + side of the Ammeter, and then a jerry rigged connection from the ammeter to the ignition and fuse box.

OHHH and the Blower Vent tube is totally melted in the middle !!! This sucker must've been HOT!!

I'm thinking he hooked up the high amp alternator to the stock wires and melted everything from the ammeter to the engine. The Neg side post of the ammeter looks toasty, thoughts?

If I were to fix this mess without pulling the whole harness, because it ran and everything worked. Would I just need to run Alt to +Batt , + Batt thru fusible link to + side of Ammeter post, then a link from ammeter to the ignition and another to the fuse box?

So above, you can see the nightmare splicing... top left White/Blue goes to fuse box (wire ok), then next to it is a splice going to the ignition (metal tie), then the blue connector splice went to the ammeter. Don't worry it was covered with electrical tape. The Black/Yellow wires are also spliced together right there (metal tie).

Lastly here's a pic of the alternator. Only one wire connected. What are my options for another single wire (since the harness wires are long gone) that mounts in the stock location, lower amps? Any help is appreciated.

 

[KingAir Driver]

Here's another alternator view. You can see the bubba'd bracket to get it to line up with the belt. The wiring that was wrapped up, blue wire wasn't attached to anything, blue wire out of harness, and the yellow had 3 splices for a ground, 2 for the horn white/black, and then grounded under the coil. arg..

 

[GHalll]

Considering GM alternator install

GM Alternator on a '78 FJ40

What GM alternator to use to convert

I just put a CS 144 alt on my 75 40. 3 wire hook up which seems to be very simple. I believe a true 1 wire goes straight to the battery but I'm no expert. 2-4 AWG wire seems to be popular.

 

[Coolerman]

That is one lucky Cruiser!
Having worked on harnesses that have suffered this fate, I can only offer this piece of advice: Find another harness before your have another fire. You are in for constant weird issues due to wires that melted together in the original fire. At random times they will become temporary shorts resulting in much head scratching. That main charge wire runs the entire length of the harness and should NOT have melted if it had the correct fusible link installed.

It's possible you could pull the harness, un-tape it, and repair all the damage but I would simply look for a replacement. If you post the month/year of your truck someone may have such a used harness. If you want to tackle this yourself, I sell all the wire and connectors and harness tape to do it. See my sig line for the link to the site.

Good luck...

 

[GA Architect]

FWIW - Per Coolerman's information, I remember running across this little jewel for a '77.....click > here <

 

[Pin_Head]

You need to replace the wires with burned and melted insulation. This could be all of the wires in this part of the harness, although it doesn't look that bad from what you can see in the pictures. The idea is to recreate the factory wiring. You could run the alternator B+ wire directly to the battery if you don't mind your amp meter not working, but use a fusible link.


The most common explanations are that the diodes in the original alternator failed or the battery was installed backwards. The fusible link is designed to prevent this type of failure, so maybe it was missing.

 

[KingAir Driver]

Thanks for the input guys! Going with a new harness might be my best bet for time and sanity sake!

@GA Architect , thanks for the link. I'll contact him to see if that harness is still available.