When the tank is full, why does the fuel light come on?

To figure out what's causing this issue, we need to understand how the vehicle calculates fuel use. We must also learn how it detects changes in the fuel tank. A fuel level sensor is a name for this system. The amount of fuel left in the tank is determined by monitoring the voltage across the variable resistor.

It consists of the following components:

1. Float Switch - A float switch is a device that floats over the amount of fuel in the tank to provide a physical representation of the amount of fuel.

2. Variable Resistor - This is attached to the float through a metal needle and senses float height fluctuations.

3. Wiper - It resembles a little windscreen wiper that glides across a resistive surface.

A metal connecting rod connects the float switch to the variable resistance, which floats above the fuel surface. With the wiper moving across the resistive material, the variable resistor's end is connected to the ground. The wiper travels across the variable resistance when the fuel level changes, causing the voltage to vary. As a result, the wiper points to high resistance while the tank is empty, and vice versa. When the fuel tank is full, the resistance is reduced. As a result, the fuel gauge can comprehend and function with this formula because it is pre-programmed on it.

As we all know, the fuel level sensor was the source of the problem. A float linked to a variable resistance board makes up the sensor. They're in the shape of little metal lines that touch the board and relay the data to the driver's dashboard fuel gauge. Due to low-quality fuel or other dangerous chemicals added to it, the metal lines rust and grow dull as they age.

These intertwined fingers are now creating gaps between the metal sheets and the float needle. They continue to separate and create gaps, resulting in erroneous measurements and fuel levels. The unusual behaviour of the fuel gauge, which confuses and irritates drivers, is discovered at this point.

This resistance is linked to the driver's dashboard fuel gauge. The fluctuating resistance causes incorrect fuel measurements, causing the low fuel sign to remain illuminated even when the tank is full. Search online for car service in Reading and book your vehicle with a professional car mechanic to have this issue repaired or relevant parts replaced.

In this post, we'll discuss a key issue that many individuals have with their vehicles. The motorist may be driving his vehicle when the low fuel sign illuminates unexpectedly. Typically, the driver will pull over to the nearest fuel station to fill up their tank. The driver is surprised to discover that he just needs half of the tank to properly refill the vehicle.

Many people confront the difficulty of why the fuel light comes on when the tank is full at some point throughout their vehicle's lifetime.

Despite how simple this problem appears to be, it can cause the motorist to become concerned when driving and fearful of running out of fuel.

Check MOT history of your vehicle and have this issue fixed before your next MOT test is due. The reason for this is your car needs to have sufficient fuel for the MOT test examiner to carry out the necessary checks but if the fuel gauge is showing you have an empty tank when it is full, the examiner can refuse to carry out the MOT test

As a result, we'll break down this problem to figure out what's causing it and how to repair it.

To avoid any danger, we should be cautious while working with any fuel parts before diagnosing and attempting to repair the fault:

To begin, you must adjust or refine the type or grade of fuel you use. This is due to the fact that contaminants and water (if present) can rust and erode the variable resistance, making an accurate reading more difficult.

Allowing the fuel tank to run out of fuel permits debris from the bottom of the tank to become lodged in the variable resistor, making it difficult to acquire the right reading.

Measure the resistance between the two terminals of variable resistance with an ohmmeter. After that, you must compare it to the car manual's full and half tank figures.

If you find a different value, this indicates that the variable resistance is malfunctioning. Try rubbing it with abrasive and rust cleaner again until you achieve the pre-determined values. After that, you may replace the sensor. If the sensor continues to give you incorrect readings, it should be replaced as soon as possible.

Another factor that might cause the sensor to be damaged is if the fuel tank lid has a tiny ventilation opening. This hole's purpose is to relieve the excess pressure. The metal needle between the float and the variable resistance shrinks and bends when this hole is closed by the fibreglass tank. As a result, the system will fail and provide inaccurate readings. If you notice your fuel tank reducing, it's time to replace the cap.