Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
what does the volts drop too ?
at idle or driving at speed ?
how long have you owned the truck ?
are you sure the battery's cold cranking amps and volts test good and there are no bad cells in that battery ?
ok if that battery is good and tested good the computers on these trucks tell the alternator when to charge and how much too and when not to charge much at all depending on the AMPS being used and the amount of AMPS that need to go back into the battery after you start the truck up
when the alternator is unplugged it just goes into charge mode by default as the computer can no longer tell it how much to charge
the odds are there is nothing wrong at all especially with everything new and all things tested good
what you are seeing is the charging system charging when needed especially after a start to recharge the battery
as for why you just started to notice this is hard to say at this point i would not do anything more as there shouldn't be anything to fix
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very hard to say why but it is charging when its being told too
that volt gauge may have just become more accurate or possibly the programming in the computer may need to be updated with current programming changes to correct the big swing of the charging and not charging
programming in the computer being updated usually will correct things like this with the updates
how are you making out ?