Electrical meltdown/charging issues

Feelstranger feelstranger at hotmail.com
Wed Oct 3 10:15:03 PDT 2007

Thanks for the details Alan.
 That make sense of the system and now I should be able to troubleshoot, if 
I get time!

----- Original Message ----- 
From: <alancordeiro at att.net>
To: "Bernie Benz" <b.benz at charter.net>; "Kneale Brownson" 
<knealeski at sbcglobal.net>; <feelstranger at hotmail.com>
Cc: "200q20V mailing list" <200q20v at audifans.com>
Sent: Friday, September 28, 2007 10:16 PM
Subject: Re: Electrical meltdown/charging issues

> The alternator needs an electric field in the rotor to generate 
> electricity (EMF) in the stator. The field is provided by an 
> electromagnet, which gets its power from the alternator itself.
> The current in the field is controlled by the regulator, thereby 
> controlling the output voltage. To keep the battery from draining into the 
> field, the excitation current is provided by a separate set of rectifier 
> diodes, which only produce a voltage when the alternator is working.
> When the alternator first starts turning, there may be a slight amount of 
> residual
> magnetism left in the rotor. Usually it is insufficient to generate enough 
> voltage to overcome the rectifier diodes forward voltage drop (1.4 volts) 
> and to begin to boost
> the magnetic field. Here is where a small "bootstrap" current allows that 
> tiny bit extra field to bring up the voltage where the alternator can wake 
> itself up from slumber.
> The ignition circuit feeds one side of the fault lamp. The current flows 
> through the lamp, into the alternator field circuit, (which at this point 
> is close to ground). As the field circuit fires up, it reaches 12 volts, 
> at which point the lamp turns off, since each
> side of the lamp is at battery voltage.
> Three methods can be used to overcome this problem.
> 1) fix the bootstrap current circuit in the lamp in the cluster
> 2) build a temporary circuit externally, feed the blue wire a small 
> current through a 2 watt lamp right after you start the car, disconnect 
> when it comes up.
> 3) rev up the car real high briefly, at very high speeds, even the small 
> residual magnetism may fire up the alternator....this last method is 
> unreliable.....but may be a good test that your bootstrap field circuit is 
> defective and the alternator is fine...
> Alan
> ----- Original Message ----- 
> From: "Bernie Benz" <b.benz at charter.net>
> To: "Kneale Brownson" <knealeski at sbcglobal.net>
> Cc: "200q20V mailing list" <200q20v at audifans.com>
> Sent: Friday, September 28, 2007 2:18 PM
> Subject: Re: Electrical meltdown/charging issues
> On Sep 28, 2007, at 9:10 AM, Kneale Brownson wrote:
>> But doesn't the wire still have to supply that ground and light the
>> bulb for the alternator to produce?
> No. The blue wire doesn’t supply anything to the alternator, the
> alternator supplies the ground or bucking voltage to the bottom side
> of the idot lite, + is always on the other side of the lite with ign
> on. Look at the schematic.
> Bernie
>> Bernie Benz <b.benz at charter.net> wrote:
>> The blue wire from the alternator is not an exciter circuit. It only
>> supplies a ground path and a charge bucking voltage to light and
>> extinguish the no charge idiot lite.
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