Amp Gauge / Alternator Questions

[Feldsine]

Hello all. My truck is a 71 C20. It sat for 15 years, and when I got it running good, the alternator started shrieking. This turned out to be the bearings which probably rusted and gave out. So I replaced the alternator with a Napa Delco Remy 62 Amp 4 wire unit.

When I installed the new one, the belt was apparently too loose even at the far end of the adjustment. That one had belt shrieking, but here is the wierd thing, at the same time as the noise, the Amp gauge would move to the right to the first mark (halfway over). When the noise stopped, the gauge went back to the middle.

So I went to Napa again and got a new belt, and put that on. That took care of the noise and adjustment, but now the Amp gauge will intermittently move to the first mark to the right, maybe hang out there a while, and come back to middle. Most of the time it hangs out in the middle, but every once in a while (every few miles) it starts moving around.

I'm not sure what's up with this now. It seemed like last night, when the amp gauge started going to the right, the lights got brighter too. I'm afraid I might start popping bulbs or something.

You guys have any ideas on this?