Replaced battery, now battery guage acting up

[chinsk]

My old megatron battery finally kicked the bucket and I went to pep boys and got one of their energizer battery with 875 cca. What I notice is when I am sitting at a light or traffic the battery needle will start dipping, but never below normal. When I rev higher though of course it goes back up. The AC is on as well when I am seeing this behavior. Any idea?

 

[aldive]

I would het out a voltmeter and take some readings.

 

[Alec]

sounds like the alternator might be going.