1990 Plymouth Voyager Alternator not Charging

Tiny
BRLRPAIRMAN
  • MEMBER
  • 1990 PLYMOUTH VOYAGER
Electrical problem
1990 Plymouth Voyager 6 cyl Front Wheel Drive Automatic

I am working on a Voyager for my neighbor that has had a Alternator charging problem, its not charging. We removed the alternator and took it to a local Auto Zone for testing and it checks out good. So we reinstalled it and started checking the wiring. So far if I put a volt meter directly off the Alternator at the positive post and the ground post I get no voltage with the engine running I disconnected the positive power wire from the alternator to the battery so I dont get ant false reading. Second I checked the green wire coming from the control module for a negative supply at the alternator and that turns to be good wile the engine is running. Than I checked the supply voltage from the blue wire to the alternator and I get a good 12v there while the engine is running. Everything checks out good to the best of my knowledge but still no charging voltage off the alternator. My instinct tells me it is still a bad alternator but tests tell me otherwise. What else could it BE?
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Sunday, January 11th, 2009 AT 10:11 AM

7 Replies

Tiny
RACEFAN966
  • EXPERT
Ok the first thing I must say is never disconnect the battery cable from a vehicle with an alternator as you can cause some serious problems right down to the computer as that is were the voltage regulator is. This test it fine for a generator but not an alternator. You need to check the ground wire for any problems it is either blk/gry or blk. You need to check the dk green wire.
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Sunday, January 11th, 2009 AT 10:37 AM
Tiny
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The dark green wire has a verfied ground when the vehicle is running, the ground wire to the motor is fine I seem to have a good ground. I never disconnected the battery from the vehicle while it was running I disconnected the positive and negative leads to the alternator then started the vehicle to test voltage coming from the alternator but I left the dark green and blue wire connected to the alternator.
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Sunday, January 11th, 2009 AT 1:09 PM
Tiny
RACEFAN966
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What did you get at the dk green wire? Let me know so we can go to the next step.
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Monday, January 12th, 2009 AT 10:20 AM
Tiny
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The wires are really dirty but from what I believe the dark green wire is at ground when the vehicle is running, and the other wire which I believe is a dark blue is at 12v with the vehicle running. I say these colors because as I traced them through the harness through the black plug behind the battery one turns into a blue and the other is a small green that gous to the control module plug next to the battery.
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Monday, January 12th, 2009 AT 10:26 AM
Tiny
RACEFAN966
  • EXPERT
OK with that either the alternator is bad or the voltage regulator is not working. Have you had a charging system test done? If not call to your local parts store and see if they do a free test and take the car in and test it that way.
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Tuesday, January 13th, 2009 AT 10:26 AM
Tiny
BRLRPAIRMAN
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I will have them do that, I was under the understanding that there is no voltage regulator in this vehicle, where whould it be?
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Friday, January 16th, 2009 AT 7:17 PM
Tiny
RACEFAN966
  • EXPERT
Your regulator is in the computer as it controls the voltage and amps needed. So if there is a regulator problem sad to say you will be replacing the PCM.
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Saturday, January 17th, 2009 AT 8:43 AM

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