Lights Dimming/low fuel light coming on

The car has 269,231 miles. A few days ago, my wife said the lights began dimming, the fuel indicator needle began dropping and rising and the low fuel light came on (with 3/4 of a tank). Thinking it was some kind of electrical issue, I took it to the local parts store and had the battery, starter, alternator, etc, checked. There was a little corrosion build up on the positive battery terminal but everything else checked out ok.
Does anyone have any idea what’s going on?

You don’t give the age of the Escort, but it must be an oldie. The battery cables themselves can go bad, internal corrosion. And there are connectors at the other ends of the cables (not the battery side, but the motor side) that can get dirty and non-conductive.

With a car this old I’d suggest replacing both the positive and negative battery cables. I think your ground connection and/or cable is the most likely problem. Don’t wait long, you don’t want to put your alternator at risk.