Alternator Changed, Battery Light Stays On, Message Also

[catalinajack]

I own a 2003 Duramax. The alternator failed while driving (voltmeter went from 14.5V to 12V). It was replaced after driving on the batteries for about 45 miles if this means anything. After replacement the "battery not charging" message continues to appear on start-up and the baattery light on the dash stays illuminated. The alternator works. When running the voltmeter indicated 14.5V and the batteries remain fully charged even after months of running with the new alternator so I think the problem rests not in the alternator. I have cleared the DTC's probably ten times but the message continues as does the battery light. What is the cuase? How do I correct the problem?

[bill190]

Well being as how everything is computer controlled these days...

 

Try "rebooting"! That is remove a cable from the battery(s) for about 10 minutes, then reconnect.

 

If that does not work, check all fuses. Your owner's manual should have information on where all the "fuse boxes" are located. Might be more than one. Could even be 3!

 

How to check fuses...

http://www.dinosaurelectronics.com/Test_Fuse.htm

 

Beyond the above and checking that you have a good battery(s), you would need a GM Factory Service Manual set to troubleshoot the problem or take it to a GM dealer for service.

 

Note: On newer vehicles there are many different computer modules besides the "engine computer". The code scanners sold at auto stores mostly can just clear codes from the engine computer. If the diagnostic code is being generated from a different computer module, you would need a $3000 Tech II scanner to clear the code. They have these at GM dealers.

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I just had the same problem. I was able to get another alternator to check the wiring and low and behold, on the plug on the alternator, the wire that sends the volt reading to the PC to indicate the battery voltage was not showing the correct amount of power...i forget what is was supposed to be. Nonetheless, even though the alternator was putting out over 14 volts, the one wire was faulty. I was able to diagnos this because I had another alternator next to me. Once I discovered the issue I just returned the bad one since it had a lifetime warranty.

 

I hope that helps.

[catalinajack]

I just had the same problem. I was able to get another alternator to check the wiring and low and behold, on the plug on the alternator, the wire that sends the volt reading to the PC to indicate the battery voltage was not showing the correct amount of power...i forget what is was supposed to be. Nonetheless, even though the alternator was putting out over 14 volts, the one wire was faulty. I was able to diagnos this because I had another alternator next to me. Once I discovered the issue I just returned the bad one since it had a lifetime warranty.

 

I hope that helps.