dwa

Hi, I’ve got an overcharging problem that has me stumped. I’ve read a lot of the posts regarding overcharging but naturally mine seems to be a bit different. I have a ’91 W350 4WD and noticed the overcharging because of the smell from the battery. Book says grounded fields on the alternator can cause overcharging, and sure enough, one of the field posts showed zero resistance between the alternator case and field post. I disconnected the wiring from the posts and rechecked and the resistance was infinite between the post and alternator case, which says the fields are not grounded internally in the alternator. I then checked the wiring and found that the dark blue wire that normally connects to one of the field posts showed to be grounded, but the dark green wire that goes to the regulator was not. Bottom line, I check the wiring back to the first splice by disconnecting the wires at the different junctions. All good back to the splice J2. I also took the regulator out of the circuit when checking and it made no difference. What has me stumped is that at splice J2, other wires besides those from the regulator and alternator are spliced in, but the components that those wires go to work find. Those include ignition switch, left engine wiring and the diagnostic connector. If a component or wire that is connected to the splice is grounded and shouldn’t be, wouldn’t that cause problems with those components as well? I mean some of the components include the air heater relays, engine controller, fuel pump, fuel heater – in other words some major components. Any thoughts or suggestions on where to go would be greatly appreciated. Sorry for such a long post, but wanted to spell out what I had already done.

wannadiesel

I would throw a regulator at it. Blue is field power, the continuity to ground you are seeing is because of all the other things it powers, not because it's shorted to ground.

dwa

Thanks for the info. I'll try a new regulator. The one on the truck is only a year old, with little driving during that year (snowplow truck). It is a NAPA regulator. From your other posts, I'll get the recommended MOPAR one. Should I run the ground wire from the regulator to the alternator body and will that help extend the life of the regulator? Thanks again for the info.

PapeCAT

I see you are quite the sparky... However I'm kind of in a hurry (fri nite double date with the mrs.) and can't read to understand all the t/s that has occurred thus far... HOWEVER:

From my experience definitely do not rule out the alternator iteself... Without much diagnostic savvy when I had this issue on my '89, I threw two V - regs at it, a battery (ruined two) and finally got around to swapping the alternator and viola...

Twisted Inc.

i would try installing an internal voltage regulator....its pretty simple to do and is supposed to be better in the long in the fact that they as supposed to last longer....i can get the part number for you tomorrow if you like....i kept the transpo box in case i ever needed another....

dwa

Twisted -- thanks, I'll look at that. P/N would be appreciated if not too much trouble.

Twisted Inc.

ok, buddy i just ran out to the garage and grabbed the box its Transpo P/N [IN8315] its just a little circuit bored looking thing that has four wires on it....you install it under the back cover of your alternator and run a 12v wire to your field post when the key is on....it can't have constant power just when the key is on....but im sure you know that already....you bend your stock two field terminals out of the way and tape them up...it has a great instructions with it in the box that even i could figure out....help this helps...[/I]