I replaced my alternator because it quit had it checked and it was bad but put the rebuild alternator in and only getting 12.6 volts.
When I replaced the alternator and took it to the parts store they tested it and stated the regulator was bad. Removed the alternator and took it in and they tested with their equipment and was told that the alternator was good. I have three ECM control boxes I know that are good and it still does the same thing 12.6 volts
A slipping belt could cause low volts, did you change the belt as well?
No but it was good only replace it in October 2017 when I had to change the engine out.
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