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Old 08-19-2006, 01:35 AM   #11
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I have had an ammeter on the battery and I have also had it on the back of three different altenators that I have installed on my car. The symptons never change between altenators I even tried a new battery today and still have the same results.
I even went as far as putting the ammeter on the feed to the fuel pump and the load does not change it stays steady at about 2 amps. When the car is running the amp input from the altenator is about 9 amps with everything turned off. At the back of the altenator it is approx 11 amps. I cant believe that three altenators are having the same problem. I am really leaning toward the P.C.M. at this point due to the fact that it controls the regulator in the altenator at least by the looks of the wiring diagram in the service manuals. I am absouloutley sure that there is no corrosion on any battery cable as I took the boots off and used a wire brush and totally cleaned them. I checked the ground buss also and it is clean and not corroded. I am totally stumped.
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Old 08-19-2006, 01:42 AM   #12
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Before you run with this thought, I would like the gearheads to chime in.

These alternators that are in our cars are internally regulated as well if I am not mistaken. I would run 12 v right to the where the the alternator get'* it'* power from the pcm and see what that gives you.

But again, gearheads, please chime in....
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Old 08-19-2006, 02:21 AM   #13
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What Cheetah is suggesting won't hurt anything. All that the PCM does is send 12 volts to the regulator basically telling it that the ignition has been turned on. Then there is a sensing voltage that is sent to the regulator usually through a fuse. All voltage/current regulation is handled internally within the alternator. Here'* a tyical description..taken from a '99 GP.

The generator provides voltage to operate the vehicle'* electrical system and to charge its battery. A magnetic field is created when current flows through the rotor. This field rotates as the rotor is driven by the engine, creating an AC voltage in the stator windings. The AC voltage is converted to DC by the rectifier bridge and is supplied to the electrical system at the battery terminal.

The generator'* digital regulator uses digital techniques to supply the rotor current and thereby control the output voltage. The rotor current is proportional to the width of the electrical pulses supplied by the digital regulator. When the ignition switch is on, voltage is supplied to terminal L from the powertrain control module (PCM) , turning on the digital regulator. Narrow width pulses are supplied to the digital rotor, creating a weak magnetic field. When the engine is started, the digital regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once the engine is running, the digital regulator varies the field current by controlling the pulse width. This regulates the generator output voltage for proper battery charging and electrical system operation. Voltage is supplied at all times from the GEN fuse in the underhood accessory wiring junction block through circuit 2740 to terminal * of the generator. This is used to provide a better battery voltage measurement. The powertrain control module also monitors the generator using terminal F through circuit 23.

The monitoring done by the PCM is generally to indicate if a fault exists. About the only external thing that I can think of to check is the fuse, and connections that supply the sensing voltage to the regulator.
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Old 08-19-2006, 08:22 AM   #14
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Very good detailed description of the alternator/voltage regulator, Archon.
nisman, based on the info you supplied, I would concentrate on inter-connecting wiring between alternator & PCM (sensing, generator turn on signal etc) or it may very well be the PCM that is at fault. It appears that you have ruled out the alternator and by the info you have given, I can't disagree. Take a close look at the C1,C2 connectors at the PCM for any corrosion at the pins or sockets.
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Old 08-20-2006, 03:15 PM   #15
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well today I did a continuity test between the p.c.m. connector and the altenator connector and it checked perfect, I was talking to a guy that works at a pontiac dealer and he told me that he has seen this issue on quite a few h bodies between 96 and 98 and they replaced the pcm to resolve the problem so I think thats what I am gonna do, I will let ya know what comes of it
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Old 10-17-2006, 05:43 PM   #16
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my 95 is doing the same thing..... did you get this resolved
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Old 10-17-2006, 06:39 PM   #17
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Hi jal0065!

Please start a new topic describing your sytmptoms ... The original author of this one hasn't posted since Aug, and likely will not answer you.

It will be better to discuss your issue in a new thread rather than in this old one. Please reference this topic in your new one by referencing the url address, if you like

Tracy
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