fuel gauge problem on 1995 F-150
i have a 95 F-150 supercab (w/dual tanks). shortly after purchasing the truck used (about a month ago) the fuel gauge reading on the front tank dropped to empty (both tanks were filled). i can switch back to the rear tank and the gauge returns to full. i know that the tank selector switch is ok, because i initially ran the rear tank out of gas, switched back to the front tank (again showing empty on gauge) and ran 70-80 miles back on the front tank. i have checked the fuse, but with a single gauge-and again its working on the rear tank- did not see a problem in the fuse area. i have a Haynes manual but little info on the sending units and related wiring. Any info on this would be greatly appreciated. i occasionally make some pretty long hauls, and although i can estimate mileage with the odometer i sure would like to straighten this out.