Charging System Issues


Active Member
May 25, 2001
I believe my voltage regulator in the alternator is toast, but I'm looking for a second opinion before I go ordering parts.

Here's the deal, The car is not charging at all. I did some research According to the info on GNTtype the alternator pin the brown wire makes contact with should be grounded when the alternator is not spinning and show about 2.5 volts witht the engine running. First thing I did was check out the dash light circut. I cleaned all the contacts and checked the bulb. I double checked the circut by grounding the brown wire at the alternator with the key on and the dash bulb lit up, so everything is good there. I moved on the the pin on the alternator, that's where I think my problem is. Not running there is no ground connection. With the engine running, there is no voltage there either. All this is pointing to a bad regulator I assume??

If so, I'm going to try the the Turbo Buicks 200 amp alternator kit since it does include a new regulator.

Your post is somewhat unclear. When you checked for voltage, was the field wire hot? Good job checking the idiot light circuit, but the wire next to it is the field circuit. I think it is hot all the time. Also, is the B+ terminal hot? If not, you have a fusible link problem. All in all, the alternator is probably bad, but it never hurts to cover all the bases. Good luck!
My Batt + Terminal on the Alt is showing the same voltage present at the battery terminal.

The pin on the alternator I checked is the same one the the brown idiot light wire makes contact with.

I'm a little lost on the field wire, What wire is this? I know of the large Batt + terminal on the back and the single brown wire plug that is the idiot light circut. Did I miss a wire? It was getting dark.
There is no field wire. The only wire on your alternator is a brown wire in the "L" cavity. This wire goes to the idiot light on the dash, and the other side of the light bulb goes to switched ignition 12 volts.
When the alternator is not spinning, the brown wire is internally grounded thru the regulator - hence, the ALT light is illuminated before the car starts. Once it starts spinning, the brown wire essentially feeds the field circuit a few milliamps to excite the field, making the alternator produce voltage and current. IF the regulator should fail, the brown wire goes to ground, causing the ALT light to illuminate while the alternator is spinning.
Without an excited field winding, the alternator won't produce anything. Ther is a FIELD terminal in the alternator plug with no terminal in it. Certain applications require an exciter feed there, but the GN does not.
Caspers has a plug-and-play harness that plugs into the alternator which guarantees that the alternator will always charge regardless of the condition of the dash light. It's a good idea to put one in your car as it will prevent you from being stranded due to a dead battery/lack of charge.
Part number 102032 can be found at

Hope this helps,
It's better, but now a new issue. :mad: I did the upgrade kit, and my volt light now works key on engine off. Start car and the light goes out and battery begins charging showing a nice 14.2 voltrs. All I fixed right...............WRONG. As soon as I get into the gas and bring RPMs above 1500 or so the dash light starts flickering and the battery voltage begins dropping into the 12V area. Go back to idle and it's charging properly again.
So now I have an RPM related charging problem. I'm hoping it's just a slipping belt. If that doesen't fix it, I guess that leaves either the brushes bouncing or a loose wire on the rotor. Correct?

Ok guys, I defer to you regarding GN charging system wiring. Field power supply is internal, regulator trigger is from the rest. good system!
Well, My first guess diddn't work. Swapped the belt today and no difference. At least I have a new correct length belt on the car now. :cool:

Still have the charging problem. :frown: I did notice that when giving a quick rev that it doesen't stop charging until the RPMs begin to fall or remain steady. While they climb, it is still charging. I'm going to order a replacement rotor in hopes that I knocked someting loose on mine while I had it apart.
check the gauges fuse

the regulator has a high and low rpm circuit in them so the reg is toast

might want to check the birdge and rectifier also.

A altnernator creates AC current and the dioides and birdge and recifer turn it into DC current . there is three sets of circuit winding in a alt one of them could be smoked to.

I really don't think you need the 200 amp kit. unless ytou have a big stereo amps ETC.. in the car you have no need for 200 amps. Why cause you can't load the eletrical system hard enuff to make it produce 200 amps.
I hope it's not the reg. That, the diodes, and the brush assembly are all new. I know through testing that my old regulator was shot, I hope my new one isn't too. I was leaning toward the rotor since that's the only old part left in the alternator. And it changes speed with RPM.

I am running a large stereo amp now and plan on adding some more so that's why I went with the 200 amp upgrade. And it was cost effective since it contained a part i needed anyway.