The Fuel Level Sending Unit (1) contains a variable resistor (3) (track). As the float (2) moves up or down, electrical resistance will change. To test the sending unit it must be removed from vehicle. The sending unit is a part of the Fuel Level Sending Unit/Sensor, located and accessible at the top of the fuel tank. Measure the resistance across the sending unit terminals. With float (2) in up position, resistance should be 20 ohms (+/- 5%). With float (2) in down position, resistance should be 270 ohms (+/- 5%).