Alternator ailments

Kneale Brownson knealeski at
Tue Jun 26 18:22:14 EDT 2007

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?

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.

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