I'm not sure if it's an alternator problem or a battery problem but in my car when I first start my car the gauge reads right at 13 volts then it will drop down about a quarter way below it and randomly jump back up. At times it even get about a quarter way from 8 volts but never gets into the red zone. Is this normal or should I start looking for a problem? My lights don't dim or anything runs and drives just fine.

 

it could be a problem with the gauge. get a seperate voltage meter and wire it to the battery and run it inside the car. see if the voltage between the gauge and the seperate voltage meter match up.