87 monte carlo altenator

1987 CHEVROLET MONTE CARLO
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BOBALBERTYJR
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Checking the altenator with a multimeter,i have 12.8 at the bat lug on the back of the alt. as well as the number two port,with or without the key on, have voltage at the number one port with key on only,but sometimes it is as low as 2 to 3 volts,or as high as 14.4 volts.With the car running on the fast idle solenoid it will continue to run with the battery disconnected,but as soon as you kick it off the fast idle solenoid it will die.Would this reflect a voltage regulator is going away,dont have the info to check the diode bridge or the rectifyer.
Nov 19, 2006 at 10:08 PM
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BACKYARDMECHANIC
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Your car has the voltage regulator built into the alternator, so if you change the alternator you also change the voltage reulator.You say you are getting 12.8 volts off the battery with the car running and no accessaries on. You should ge at least 13.2 (at a bare minimum) with the accessaries on and higher with nothing on. If you replace the alternator I think you will fix the problem.
Backyardmechanic
Nov 20, 2006 at 1:54 PM