I've got a serious issues with my charging system
on my 77 dodge van.
Yesterday I was going and the van stopped running. Pull off the road and it
wouldn't start, just crank, nice. I looked around and found the wire to the
field side of the alternator was fried up thru the harness to the factory
slice that goes to the ballast resistor and the voltage regulator. I have a
wiring diagram. I unhooked the plug from the alternator and it started right
up. I drove it home with no charging system.
I replaced the wire, from the splice to the field side of the alt and it
started right up, thought I had it fixed. Let it run it was charging, nice.
I taped up the harness, secured all the wires. I'm about ready to take it
for a test drive and the Ampmeter pegs negative and fried that wire
again,burned thru the electrical tape in a second. I have melted
insulation, just that wire almost to the bulkhead plug in the harness. You
should have seen the smoke, almost had a fire. Took off the wire again and
it started right up.
I had the alternator checked it's fine. I isolated everything, ballast
resistor, voltage reg, battery, ignition control mod and the alternator is
out. When I go to the pos side of the battery connection with it unhooked my
meter reads ground also when I go to the factory splice I also read ground.
When I put my meter to the pin of the bulkhead connector I read ground. This
is the wire that was burnt. That wire goes to the factory splice, and to
ballast res and center point of the voltage reg and the field side of the
alternator. I don't think I should have a ground there!!! I was going to
disconnect the wire from the ignition switch, that where it goes in the
passenger comp, and see what I have. I need to go in thru the radio hole to
get to it. I haven't done that yet. I looked at disconnecting the plug on
the firewall, been there a long time.
It seems like if there was a short there I would see it all the time and the
van wouldn't run. I ran it for 10 minutes before I had that surge that fried
the wire.
Here's what I've got on the alternator. fields to case needle pegs, batt
term to case and fields reads 40 ohms
I'm leaning to a bad alternator, original equipment.
Today I hooked everything back you, don't have the alternator back in, the
van started and ran fine, no charging
I could sure use some help, what do you think?

Shorts can be intermittent. Yours certainly is!

Keep it simple (at least at first). If the van runs fine (and there is no smoke) with the alternator disconnected, then it's likely you have an intermittent short in the alternator. Start there.

- Mac

The alt is orginal equip. I don't mind buying a alternator, if that the problem. The big thing is how did that wire burn up like that, twice and didn't even trip a fuse. There had to be some major current there to do that and I don't want to just put the old alt back because then I haven't done anything, except the wire. What else could it be.

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I do not have a manual for your van so this is guess work. J2 14dbl ignition run circuit was originaly portected by Fusible link hypalon wire. Some body replaced it with plain wire. Install your own in line fuses before altenator and voltage regulator and any were else that might cause trouble.The fuse will blow preventing fire and will help in figuring out whats wrong.

Below is a link to a simple description of how an alternator/charging system works. The diagram at the bottom of the page is most helpful.

Being that the field wire is the one that is burning up, my guess is that you have an intermittent short internal to the alternator, causing it to draw so much power that the wire goes up in smoke.

By all means, add a fuse to that circuit!

But sometimes the only way to troubleshoot an intermittent problem like that is to replace a suspect part (like the alternator) and see if the problem goes away.

http://alternatorparts.com/understandin ... nators.htm

- Mac

Thanks for all the help. I've decided to replace or rebuild the alternator and install a 30 amp in line splice to prevent further damage. I checked out the alt and the field terminals read ground to the case, I think thats the problem.

I'l let you know how I make out. thanks again

Bruce

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You are lucky it was only one wire. I had my alternator go bad, and the wire burned the entire harness, with a fire. Needless to say I didn't have a fusible link as it was all original factory wiring.

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63 Dart GT Convertible

J2 14DBL run circuit on most mopars. 14 wire gage DbL means dark blue. 30 amp way to big 15 more than enough.

Guys thanks for all the help. I took the alternator to a guy to rebuild it, I didn't want to lose my core. He tested it, it was fine. He looked around and saw that the insulator between the screw and the terminal was missing, rotted away. It was shorting to the alt, only sometimes. When I got looking around after it happened, I noticed that the terminal was loose, so I tighten it. Now I have a direct short all the time. That's what burnt the wire. So we replaced the $.01 part and everything is fine. I can't believe that a $.01 part almost burnt up my van!!

thanks for the help

Bruce

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Another one cent electrical melt down happens when a glass screw fuse is replaced with a penny in an old residential service panel…

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC