Updated at: 31-08-2022 - By: Lucas

Your low fuel sign came on, and you ran to the nearest gas station to fill up, only to find your tank was still half full. When a driver’s fuel gauge indicates that the tank is empty when there is still plenty of gas in the tank, this can be misleading.

You can learn everything you need to know about why and how to stop your car’s fuel light from coming on at random in this post.

What Triggers The Low Fuel Light?

Why Is My Gas Light On When I Have Gas (1)

First, let’s take a look at how your automobile keeps track of how much gas is left in the tank.

Every vehicle contains a fuel level sensor to keep track of how much petrol is left in the tank. Three main components make up this sensor system. wiper, resistor variable, and float switch. Foam is used to make the float switch, which floats on top of the fuel in the tank.

A variable resistor is attached to the float switch, allowing this metal board to feel the fuel’s height and pick up on any changes. A small wiper is also included, and its job is to travel over the resistive material and across the resistor board.

Metal rod voltage changes when wiper moves across variable resistor and variable resistor voltage changes when fuel tank level changes. Depending on the state of your fuel tank, the small wiper will indicate low resistance or high resistance.

Having a full tank of gas is equivalent to having less resistance on the fuel gauge, and vice versa.

Low-fuel warning lights will come on in your car if the sensor’s wiper shows significant resistance. When you refuel, the sensor’s resistance will decrease, and your fuel gauge will sound a warning.

Why Is My Gas Light On When I Have Gas?

Why Is My Gas Light On When I Have Gas (2)

When a driver has just filled up their tank and the low gas sign comes back on, it’s understandable that they might be perplexed. It’s easier to understand why your gas light comes on now that we’ve described how the fuel level sensor works.

When the low gas light comes on when it shouldn’t, it’s usually due to a problem with the sensor. The following are some of the more typical explanations for why this is happening:

Old and damaged variable resistor

A metal needle and a variable resistance board make up the variable resistor. Corrosion can cause the needle’s thin metal lines to dull and wear away over time. Cheap gas and toxic gasoline additives might also be to blame for this type of damage.

For correct fuel gauge readings, corrosion of the needle lines may prevent them from touching the resistance board, which is a crucial stage in the process.

Damaged float sensor

It’s possible that the variable resistor is causing harm to the float sensor. Incorrect fuel gauge readings might be the result of a broken or malfunctioning component of the fuel level sensor system.

Fuel gauge malfunctioning

The gasoline gauge itself may be faulty, rather than the sensor in the fuel tank. The sensor in the fuel tank is pre-programmed to provide readings to the fuel gauge, making it easy to use. There may be an issue with the fuel gauge that requires a professional examination if your fuel light is on when your tank is full.

Fuel tank ventilation hole is blocked

It has a small opening at its apex for ventilation. It is possible for this hole to get obstructed and cause harm to the tank. As a result of shrinkage in the fiberglass tank due to a clogged ventilation hole, metal needles that move across the variable resistance board may be bent.

If this occurs, the sensor will not be able to provide the fuel gauge with correct values.

How To Stop Fuel Light Coming On When There’s Fuel In The Tank

Why Is My Gas Light On When I Have Gas (1)

There are many reasons why a vehicle’s low-fuel warning light comes on when it does not need to. If the fuel sensor is destroyed, the values on the fuel gauge will not be accurate.

The following steps should be taken to protect your car’s fuel level sensor:

Use high-quality gasoline

A fuel sensor’s needle and small prongs on the variable resistance board are particularly vulnerable to damage from cheap gasoline. Water in low-quality gas can lead to rust and corrosion in metal components.

Never drive on ’empty’

The only way to keep your automobile running on pure willpower is to keep driving if your low fuel sign comes on. Running your automobile on the last of the gas in the tank can result in fuel that looks like sludge.

The fuel level sensor can be damaged by the thick consistency of the fuel at the bottom of the tank as it rolls over the surface.

Check the ventilation hole

The gasoline level sensor can malfunction if the tank’s ventilation opening is obstructed. Checking that the little hole at the top of the gasoline tank is not blocked with dirt or accumulated debris may be advantageous on a regular basis.

You should be able to keep your fuel level sensor in good working order by following the methods outlined above. Even if you can’t use this information now because your sensor is broken, it’s something to keep in mind for the future.

Using this strategy, if your low fuel light comes on even though you know you have enough fuel in the tank, you may be able to rectify the problem:

Remove the whole gasoline tank assembly in the first step. It’s possible that you’ll require the help of an expert for this task.

Step 2: Connect the red and black cables to the gasoline tank assembly’s two terminals with an Ohmmeter. To figure out which two terminals the ohmmeter should be connected to, do some study on your car.

Step 3 Verify that the Ohmmeter is set to display either ‘Ohms’ or the Greek letter Omega, which stands for zero.

4th Step: Ensure that the fuel sensor float is lowered and take note of the Ohmmeter’s reading.

This is the final step. The float sensor should then be raised. When fuel is put into the tank, this is exactly what happens. With each upward movement of the sensor, the Ohmmeter’s reading should drop.

It’s possible that the problem isn’t with the fuel level sensor if steps 5 and 6 show the expected results. There may be a problem with your fuel gauge that requires professional attention.

Step 7: Replace the sensor if the Ohmmeter’s reading remains the same whether the sensor is raised or lowered. Your sensor can be replaced at home with the help of YouTube instructions and car-specific forums, or you can take your vehicle to an auto shop.

Removing the sensor and cleaning it with a little brush and rust remover is an option if you’re not in a hurry to replace it. If the reading doesn’t change from the first time, you’ll probably need to replace the sensor.

The ninth step Although using an Ohmmeter may appear complex at first, it is actually rather simple if you have a basic understanding of how it works. The next video provides step-by-step instructions for replacing a gasoline level sensor if you prefer that method.

It’s unsafe to drive without a functioning fuel tank sensor. Your car could break down at any time if you don’t know how much gas you have left in the tank

A dirty and sludgey fuel tank can cause your automobile to overheat and malfunction if you run it for long periods of time on little fuel.


How do I turn my low fuel light off?

Getting gas is the quickest and easiest way to turn off the low fuel light. There may be a problem with the fuel level sensor if the light comes on even when the tank is full.

Make sure your fuel level sensor and all of its components are in working order if you can’t turn off the fuel light. It’s time to consult a mechanic if your low fuel light won’t go off despite the sensor being in perfect functioning order.

Can you fix a fuel level sensor?

The fuel level sensor can be repaired. To replace the variable resistor’s small metal wires if they’ve been broken, you’ll need to do so cautiously. If you don’t get the right wires, you’ll have a hard time connecting them to the resistor.

First, thoroughly clean and degrease all of the sensor’s components to remove any residue. To ensure that the sensor is working properly, you can use an ohmmeter to conduct a simple test.


Not only is it inconvenient, but it may also be perplexing to have the gasoline light come on after you have just filled your tank. The gasoline level sensor in your vehicle’s fuel tank is a common cause of this problem.

If your low fuel indicator is on even if you have a full tank, we’ve explained why in this article and supplied you with a few fixes. We hope this information is helpful and that you can fix the sensor and get rid of the bothersome fuel light in no time.