Alternator not charging?

LESLIE BRADLEY

MEMBER
2007 CHEVROLET EQUINOX
6.4L
FWD
AUTOMATIC
120,000 MILES

I replaced my battery w/a used one & once I start it the volts start out at 14.1 then drops down to 12.9ish. It has never done this in the past. Is this normal?

Saturday, January 24th, 2015 AT 6:10 PM

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

This is possible that this is normal but we need to do some testing to find out.

We need to perform two tests to start. First is to test the alternator and then the battery. The fact that this is a used battery is concerning but that may not be an issue.

https://www.2carpros.com/articles/how-to-replace-an-alternator

https://www.2carpros.com/articles/car-battery-load-test

Also, are there any issues with performance or is this just a concern you are having because you are seeing it drop to 12 volts.

This charging system is on what is called a duty cycle. Basically when the load or demand is high the alternator puts out a higher voltage.

I attached all this info below on how to check this and the chart that shows the approximate output voltage based on the duty cycle.

Please run through all this material and let us know if you have other questions.

Thanks

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