1991 240 volvo, water temp guage and fuel guage occasionally fluctuate. In the past, the alternator ground wire was failing. I replaced it three weeks ago. This time, I checked the alternator output voltage with a multimeter, and everything looks normal. What other items could cause the fuel guage to fluctuate from 1/2 down to nearly empty (top of orange zone), then back up to 1/2, in 2-3 minutes?

[[ southern fried volvo '91 240 164k mi ]]