Electrical issues - Mainly alternator based

[chappys4life]

A few months ago I picked up 70 gmc c1500. Unfortunately it has had a lot more gremlins then I was hoping but working to slowly fix them. One of the biggest issues is wiring. I looks like a drunken monkey has attempted to update the truck when they added headlight relays, si alternator, classic auto air, and a radio. The ac main feed wire was jumped off the cigarette lighter and used a wire nut. I think a electrical fire or overload happened as behind the cluster there where a lot of melted wires that where brittle or exposed wire sections. I cut the wires back to fresh copper then soldered in new replacements with a new ignition switch. The speaker wires where twisted to the stereo then taped with no connector. Now I am trying to fix the alternator wiring and go to a 12si as it sounds like the 10si bearings are going.

I have a 12si 95 amp alternator and my plan was to run a new 6 gauge wire to the battery with a inline 125 fuse and ditch the starter connection as nothing else is connected. When I was looking at the alternator I saw a wire going to the starter and another connected to the bulkhead plug on the firewall driver side. Thanks to mad electrical I am learning a lot how chevy did it (I have worked on more fords so a slight learning curve but not bad). From what I can tell the wiring from the original generator to voltage regulator burned up (see pic below) and someone did a conversion and but only 1 wire is in the 2 plug connector (see pic).

So now I am rethinking life and want to make sure it sounds like a sound idea until I order a new wiring harness. I am in the middle of building a 55 chevy that is killing my garage space so this is a slight cleanup and get by until I can pull it in the garage and take my time.

The plan is:
- take red wire from alt that attaches to bulkhead for main power into the fuse panel add a 16 gauge fusible link and connect it to a junction terminal on the firewall (also replacing most of the wire as it looks melted and no fusible link currently)
- run 6 gauge wire from alt to battery with 125 inline mega fuse
- alt connector #1 terminal 6a 50v rectfier diode #2 terminal jump to batt post to by pass any other junk wiring.
- add constant power relay 85amp to hook to the battery for big power items like aftermarket ac, autometer gauges, then trigger with switched ignition probably from fuse panel for now

I already replaced the fuel line and filter just a pic before I got to it.
Also what is the terminal block in the last pic used for?

[54blackhornet]

My first suggestion when I read about electric issues is to go to Mad Electric. Excellent info on how you should proceed on upgrading the factory wiring. You seem to be doing well on identifying the major issues that need fixing. One off topic thing ! Please replace that glass fuel filter with a metal one. Plenty of stores about them breaking open under heat and vibrations…Jack..

[chappys4life]

Originally Posted by 54blackhornet

My first suggestion when I read about electric issues is to go to Mad Electric. Excellent info on how you should proceed on upgrading the factory wiring. You seem to be doing well on identifying the major issues that need fixing. One off topic thing ! Please replace that glass fuel filter with a metal one. Plenty of stores about them breaking open under heat and vibrations…Jack..

2nd to last line its been replaced. First thing I did was just using a old pic of the alt when I first got it.

[PbFut]

How original do you want to be. Do you want original battery meter to work as designed or convert to volt meter. Will you be using heavy load items like elec fans, off road lights or bags? All come into play when designing your system. Given you found damaged harness under dash I hate to be bearer of bad news but you probably should replace the harness. Cutting out sections leave compromised remains. Do it once and do it right.

[bry593]

I use 30 amp midi fuses instead of fusible links. I've got two of these fuse holders screwed to my passenger fender and then a 6 gauge wire from the positive battery cable to the fuse holders. The fuse holders are bussed across the battery side using a piece of 3/8" copper tubing I smashed flat and then drilled.

https://www.littelfuse.com/products/.../midi-498.aspx

One of the fuse holders runs the normal GM circuits. The second runs my radio, amplifier and trailer light / power circuits.

I actually had one burn out not too long. The Chinese tachometer decided to fry out and it pulled enough amps to fry the 30amp midi.
Note that GM did not put a fuse on the tachometer power wire (pink), so I put a 5 amp AGC fuse inline for added protection.

For battery cables, I used late model Chevy cables. They are 2 gauge with 6 gauge secondaries. Can't remember what they came from. Maybe a Tahoe or something like that.

[bry593]

Originally Posted by PbFut

How original do you want to be. Do you want original battery meter to work as designed or convert to volt meter. Will you be using heavy load items like elec fans, off road lights or bags? All come into play when designing your system. Given you found damaged harness under dash I hate to be bearer of bad news but you probably should replace the harness. Cutting out sections leave compromised remains. Do it once and do it right.

I agree it would be smart to replace the dash harness with a new one from American Autowire. Don't get me wrong, if the damage is minor, go ahead and fix it with matching color and gauge GXL wire. But it sounds like yours is pretty toasty.

[chappys4life]

Originally Posted by PbFut

How original do you want to be. Do you want original battery meter to work as designed or convert to volt meter. Will you be using heavy load items like elec fans, off road lights or bags? All come into play when designing your system. Given you found damaged harness under dash I hate to be bearer of bad news but you probably should replace the harness. Cutting out sections leave compromised remains. Do it once and do it right.

The plan is to put in a new american autowire harness for sure. I am just trying to make it work for now as my driver while I am doing floors in my 55. The floors where not too bad but after pricing patches it made sense to do a whole 1 piece which is taking longer than I hoped.

[chappys4life]

Got a slight start. Did the main harness wire with a fusable link to a continuous duty solenoid. Figured it could sit with the battery connection for the solenoid for now. did a 6 gauge to the battery. The resettable breaker for the new 12si alt . The cvf bracket arrives tomorrow so i did rivet nuts and mounted it to get ahead.

I still plan on doing a harness just trying to find time to balance all of the projects needing attention.

[LS short box]

Not really (or at all) but when you talk about a total wiring mess is my a 67 Nova project I bought.
PO got totally screwed on a LS swap. See pic.
When I done it looked like this.
I used a Painless 21 circuit universal wiring kit.
On 68 C10 LS swap project I replaced all the wiring but saved the stock end connectors and spliced them into the Painless harness.

[chappys4life]

Oh its a mess. The wires where melted with exposed wire super corroded and green. Think more electrical fire less unorganized.

Will pull some wires out of the garbage and snap a pic

[Rust_never_sleeps]

I put a 20A auto-resetting breaker on each headlight relay, per kit instructions.
Mine feed off that terminal block on the fender. Not sure if your guy didn't use breakers or just went around that terminal.

Kinda sounds like your PO just re-used the wires once he got them to stop smoking, so they corroded where the insulation was compromised. Zero chance of that biting anyone in the ass down the road

[Rust_never_sleeps]

P. 594 of the book shows what that terminal block might have looked like before Smokey started rewiring things: