1998 chevy k1500 5.7l 105a alternator. replaced alternator and belt. slowly stops charging. worse the more things you turn on. battery shows 12.8 volts with engine not running . when first charging starts at 13.8 and goes all the way down to 12.5.
At idle the alt shows 12.5 ?
How about at 2000 RPM....does the voltage rise with increased engine speed?
If no increase in voltage with higher RPM........the alternator may be defective.
Remember....if battery is low and you add the load of all accessories the voltage may be low at idle speed until the battery is charged up.....this would be normal under this condition. Once the battery is charged the alt can handle the load of the accessories at idle and should be able to keep voltage up.
Also......a defective battery could be taking all the alt has got to give.....resulting in a low voltage reading.
We would like to see approx 14.5 volts when vehicle is running.
Now change the sulfated batery for a new one.
Vitally
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