Didnt hook it up right, fried the alternator, i need help...

[Caleb]

ok i finally got the old 66 d100 running with the new la318 in it, but i have a problem. the wiring harness that was on the truck when it had the slant six in it only has one field wire going to the alternator. i bought a new alt for a 74 charger, because thats where the engines from, and put it on, but it has two posts for field wires. i figured that it would work if i only used one wire, seeing as how its all i have, but it still wouldnt charge. then i got the great idea that maybe the other post is a ground, so i ran a ground wire from that post to the a ground screw on the regulator to ground it. it worked then-it was charging great, but thirty minutes later, my ground cable to the battey blew up. it literally melted and blew off of the battery. also, im pretty sure the alternator is fried. so now im coming to yall, my friends. do i need an alternator that has only one field wire post, or if not what do i do with the other post? does anyone have any suggestions here? thanks

[Hotfoot]

Ouch.

Mine had a small fire years ago and I have not had the time to get it straightened out! If you blew the Bat cable you may have fried some other stuff too!

[Hobcobble]

Look for any post from "Jeffc" and you'll see an ImageEvent link to his tech
section. In that tech section, you'll see a diagram for the single and the dual
field alternators. At minimum, you'll need to make sure your '74 alternator
is not fried and that you're using it in conjunction with the newer '70/'71
voltage regulator. Get a heavy gauge replacement ground cable and also
make sure you have an adequate ground strap between the engine block
and firewall. Considering what happened, I'd also suggest inspecting your
wiring [engine compartment and under-dash] for possible melted portions.
If that '74 alternator is of a very high amp output [90+ amps], you're
approaching "harness-meltdown" territory
John

[MountainMoparRobin]

I would strongly urge ya to do what Hobblecobble said for help in wiring the altenator, I believe you may get lucky on the altenator though and it probably is still good, but you will need the newer solid state regulator from the 70-71 error, also you'll have a ground at the rear of the engine going to the firewall nad then another ground at the front of the engine from the block to the frame, for sure your going to have to replace the wires in the charging system at a minimum, good opportunity to upgrade to bigger wires

[Jeffc]

Robin and John are on the right track......
If you do have one of the late big amp output alts then you really need to do a system up
grade (mad wiring by-pass) were you run a large 8 gauge wire strait to the battery from the
alt, by-passing
everything but the starter relay (or even strait to the battery) and install a voltage gauge
so you got some idea what your system is doing...(still need to leave everything else the same)

However the way you hooked up a 2 field wire alt is correct for the old one field wire regulator,
at the alt- ground one
and other to reg.
Should not cook the system.....
How far down was the battery when you fired it?
Did the battery have the right amount of fuild in it?
How old is the reg?

[OleRed66]

If you have the old alternator, reinstall it.