98 TJ with 4.0 and automatic, check gauge light came on today at lunch, looked at the amp gauge and it was almost at zero. Pulled over and popped the hood, didn’t see anything. Went to start it back up and the gauge was at almost 12 It stayed like that for about two miles then started going down again. Went to Advance Auto Parts to have charging system checked. The battery checked low but ok. The alternator was putting out over 13. Started it back up at Advance and the gauge went back up again and this time the check gauge light went out. Went about ½ mile and it came back on. I took it to the house and will investigate after work. Anyone have an idea where to start?