The fuel-sending unit is a potentiometer that is adjusted by a float attached to a rod fair passion the float in a toilet bowl.
How the Fuel-Sending Gauge Works
The gauge has four electrical points. It has one terminal for battery acceptable, a ground, an blaze and the expression, which is the wire to the sending unit.
Location
The sending unit is located in the fuel cistern, and in late-model cars it is normally attached to the fuel pump carrier bracket. The bracket contains both the fuel pump and the sending unit; on the contrary, Everyone can be replaced separately. The wires to the sending unit are intermingled with the wires for the fuel pump in a daily electrical connector at the rear of the vehicle.
When the fuel in the cistern drops in constant, the arm with the attached float correspondingly drops, which changes the size of resistence in the potentiometer. It is a incomplex mechanism, although all the contacts must be ideal Disinfected and tight in that the solid development relies on resistence metering. A malicious ground can causation a deviation in resistence that the gauge would display.
The ground on the gauge must be ace for the gauge to office genuine. Whenever credible, the ground should be attached to the frame.
All present-day vehicles account a printed progression board. To test the gauge, the identical method lines on the board must be probed. It is not exhausting, however provided a inaccuracy is initiate in the board, it should be replaced. Trial from the gauge trail to the connector on the board for continuity to research the board for operational readiness. From the board connector to the electrical connector on the tank to the sending unit can be checked for continuity. To eliminate the gauge in a failure, just ground the signal wire at the electrical connector at the tank while the key is on. The gauge should go to full. If it moves the gauge, then check the ground for the fuel pump. The power to the sending unit comes from the gauge through the signal wire and passes through the potentiometer and to ground. There will be 12 volts going in via the signal wire but only 4 volts coming out of the sending unit potentiometer going to ground, depending on how full the tank is.
Remember, when changing a sending unit, it must be compatible with the gauge in terms of ohms. If a factory replacement is called for, there should not be a problem, but for those that are replacing both units, this applies.
