Hey guys, I've got myself a 1989 Camaro RS.

My alternator gauge is giving me weird readings. If I start the car when it's cold, I get the usual reading of a little over 13 on the gauge. After it warms up a bit, however, it will fluctuate, all the way down to 8, between the middle of 13 and 8, or right below 13.

I know it's still charging the battery, because if I shut it off, the car turns over insanely quickly (full battery, so to speak). The battery is kind of old, though. The previous owner replaced the alternator about a year ago, too.

So, what could be causing my gauge to read oddly, but the alternator keeps charging correctly? I've taken an alternator tester to it when the gauge reads around the 8 mark, but it's still giving a good charge.