Alternator question

This refers to a 1994 Chevy Corsica with a 6 cylinder engine.

Is it possible for the car's computer to send a signal to the alternator
telling it to increase the voltage output? Does the alternator have a
variable-voltage regulator that is controlled by the computer?

The reason I am asking this is because an indicator light on the instrument
panel sometimes comes on that indicates an electrical problem. The light is
red and is shaped like a battery. When the light comes on I am reading 16
volts at the cigarette lighter jack with a voltmeter. When the light goes
out it reads 14 volts. It comes on and off intermittently. I know that the
battery is good.

To repair this problem, I purchased a new alternator (which contains an
internal voltage regulator) today and installed it. I started the car and
everything was fine for a couple minutes, then suddenly the indicator light
came on and was MUCH brighter than before and a loud noise came from my
radio speakers. I immediately shut the car off and checked my work and
verified that I had properly installed the alternator, which I had. I
started the car and the same thing happened again. I immediately shut it off
to prevent damage to the car. I then disconnected the heavy red wire from
the alternator to prevent the alternator from sending electricity to the
car, started the car, and checked the voltage output at the alternator. It
measured only 9 volts, a minute later dropped to one-half volt, and has not
come back up since.

I don't know if this new (actually remanufactured) alternator is defective,
or if something in the car such as the computer is sending a signal to the
alternator telling it to put out way too much voltage. I noticed that there
is a 4-conductor plug that plugs into the alternator, so I am suspicious
that the computer is controlling how much voltage the alternator puts out as
if the alternator has a variable-voltage regulator that is controlled by the
computer. Can someone please tell me what may be the problem? Thank you.

"j" > wrote in message
t...
> This refers to a 1994 Chevy Corsica with a 6 cylinder engine.
>
> Is it possible for the car's computer to send a signal to the alternator
> telling it to increase the voltage output? Does the alternator have a
> variable-voltage regulator that is controlled by the computer?

Chrysler and Ford may have the regulator in the PCM or ECM. The
GM alternators that I know about have the regulator inside the alternator.

There could be exceptions, I guess.

"j" > wrote in message
t...
> This refers to a 1994 Chevy Corsica with a 6 cylinder engine.
>
> Is it possible for the car's computer to send a signal to the alternator
> telling it to increase the voltage output?

No.


Does the alternator have a
> variable-voltage regulator that is controlled by the computer?
>

No.


> The reason I am asking this is because an indicator light on the
> instrument
> panel sometimes comes on that indicates an electrical problem. The light
> is
> red and is shaped like a battery. When the light comes on I am reading 16
> volts at the cigarette lighter jack with a voltmeter. When the light goes
> out it reads 14 volts. It comes on and off intermittently. I know that the
> battery is good.


How do you know the battery is good ? Did you have it tested ?


>
> To repair this problem, I purchased a new alternator (which contains an
> internal voltage regulator) today and installed it. I started the car and
> everything was fine for a couple minutes, then suddenly the indicator
> light
> came on and was MUCH brighter than before and a loud noise came from my
> radio speakers. I immediately shut the car off and checked my work and
> verified that I had properly installed the alternator, which I had. I
> started the car and the same thing happened again. I immediately shut it
> off
> to prevent damage to the car. I then disconnected the heavy red wire from
> the alternator to prevent the alternator from sending electricity to the
> car, started the car, and checked the voltage output at the alternator. It
> measured only 9 volts, a minute later dropped to one-half volt, and has
> not
> come back up since.


Check your battery to make sure it is good/fully charged. Also check your
battery cables for a good, clean connection. A fully charged battery should
read around 12.6 volts. A fully discharged battery would read just under 12
volts ( 11.8 - 11.9 volts ).

Try measuring battery voltage at the battery terminals and see what you
get. Also check your battery cables are clean and tight. To go from 9 volts
down to 1/2 volt indicates a bad battery or a poor conection.

It's also possible that your battery is bad and causing the alternator to
overcharge.



>
> I don't know if this new (actually remanufactured) alternator is
> defective,
> or if something in the car such as the computer is sending a signal to the
> alternator telling it to put out way too much voltage. I noticed that
> there
> is a 4-conductor plug that plugs into the alternator, so I am suspicious
> that the computer is controlling how much voltage the alternator puts out
> as
> if the alternator has a variable-voltage regulator that is controlled by
> the
> computer. Can someone please tell me what may be the problem? Thank you.


The alternator is NOT controlled by the computer. The alternator is
controlled by the internal voltage regulator.