Scorpio (Gauge)

Apply 13.5 volts to stud "E" on rear of instrument cluster. See Fig 1 . Apply ground to stud "C". Place a 250-ohm resistance between studs "F" and "C". Gauge pointer should position itself between calibration dots at "LOW" level. Remove resistance.
Place a 19-ohm resistance between same studs. Gauge pointer should position itself between dots at "full" level. Remove resistance.
If pointer lies between calibration dots, check fuel sender. If pointer lies outside upper or lower calibration dots, replace fuel gauge assembly.

Fig 1: Rear View of Scorpio Instrument Cluster

Courtesy of FORD MOTOR CO.