Alternator ailments

Bernie Benz b.benz at
Tue Jun 26 19:14:11 EDT 2007

On Jun 26, 2007, at 3:22 PM, Kneale Brownson wrote:

> OK, putting the car on the hoist so I could get to the alternator  
> more easily, the voltmeter starts reading "normally" again, jump  
> post voltage is 13.8.
> So I have an intermittent voltage regulator function?   Could that  
> be a bad wire (other than the famous "blue") to the alternator or  
> something internal to the alternator or the regulator?
Yes. The regulator ground connection thru one of the attachment  
screws. Remove the reg, check the brushes and clean up the mounting  
surfaces and screws. Reg is most likely good, just its ground to the  
alt. frame.

> Bernie Benz <b.benz at> wrote:
> On Jun 26, 2007, at 1:59 PM, Kneale Brownson wrote:
> > Finally got a chance to test my charging system that started acting
> > up while we were in Columbus, OH, over the weekend but managed to
> > get us home.
> >
> > With the engine off, the battery reads 12.5 volts. Same reading
> > for the positive terminal post under the hood.
> Implies no current flowing between the two points.
> >
> > With the engine running at idle (voltmeter in car reading ~12),
> > the reading with my multimeter is 12.17 at both the battery and the
> > jump post.
> Still no current flowing.
> > I presume that means the regulator ain't regulating properly, but
> > the dreaded wiring "weld" in the passenger footwell is passing on
> > its voltage without any resistance.
> Resistance only impedes current flow, not voltage.
> >
> > Is it possible the "exciter" circuit (blue wire) would be the
> > culprit?
> No! The blue wire is not an exciter circuit. It provides a ground
> path and a bucking voltage to respectively lite and extinguish the
> alternator warning lite, among other unrelated things.
> I’d say that you have a bad regulator or regulator ground path.
> Bernie
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