How Does a Fuel Level Sensor Work?

Fuel Level Sensor

Last Updated on December 6, 2021 by Yusuff Adeniyi

How It Works

It is important for drivers to keep track of how much gas they are using and when they should refuel. The sensing system (also known as the sender) and the indicator are the two primary components (also commonly referred to as the gauge).


Sensors in the fuel tank are made of foam and metal rods, and a variable resistor is used to control the actuation of the metal rod. As the float moves over the resistive material, a small wiper (similar to a very small windscreen wiper) moves over the resistive material to read the fuel level in real time. Due to changes in fuel levels, the float moves across the resistor, resulting in an increase or decrease in voltage. Wiper orientation causes the resistor to experience the highest resistance when tank is empty. The wiper is also as far away from the resistor’s ground end as possible at this point. The indicator receives the new reading after the change in current is sent to it.

How It Works In Automobile

Fuel level sensors in automobiles, on the other hand, can be inaccurate, especially when driving with a full tank. Float rises, wiper goes back to the ground end of the resistor, resulting in a low resistance and high current through the sensor, as shown in the figure. The resistance changes as the float falls in height, but the gauge often stays on ‘full’ for a long time. Due to the fact that the fuel tank blocks or limits the reach of the float’s actuating rod when it’s full, the float sinks into the fuel, the float becomes submerged when the tank is full. When the fuel level reaches a point where the float is able to sit on top, the resistance changes, resulting in inaccurate readings.


As a result of this, the gauge may indicate an empty tank even though there is still some fuel remaining inside.

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