My guess would be your battery has a cell that is going dead. I would suggest replacing it and I bet you will solve that problem. You can get a higher amp Delco that will replace your current alternator. I can build one in whatever amperage range you like in the 70-100 amp range in a one wire unit that is really nice. Does away with some of the wiring, you just need it to make a path to the guage and then to the battery. Private message me if you want more info on this.
Ken
