Top 5 Reasons Why Your Fuel Gauge Not Working (And How To Fix It)

When your gas gauge doesn’t work right, it can cause big problems. You might end up stopping at the gas station more frequently than your real demand. This means your vehicle will carry extra weight from the unnecessary gas, and you might have to take detours to fill up. Learn the most common causes of the fuel gauge not working correctly.

When operating your vehicle, you heavily depend on a functioning fuel gauge that informs you when it’s time to refuel. When the fuel gauge becomes faulty, every trip becomes uncertain, and you can never be sure if you have sufficient fuel to reach your destination. If this crucial component ceases to work properly, it’s essential to understand the causes of its malfunction or inaccuracy.

This article explains the most common reasons for a fuel gauge not working and how to reset it.

How Does a Fuel Gauge Work?

Your fuel gauge is what tells you how much fuel you have in your tank and if you need to fill it up. It might seem like a simple part of the vehicle, but it’s actually a complex and vital part of the vehicle that may go bad over time.  

The fuel gauge system of your vehicle typically has three main parts: the fuel gauge on your dashboard, the fuel gauge sender sensor, and the wires connecting them.

Fuel gauges operate on the electrical resistance principle with a float attached to a metallic rod as the internal ‘needle’.

Here’s how it works: Inside your gas tank, there’s a float that goes up and down as the gas level changes. This float is connected to a variable resistor by a metal arm. When the float moves, it changes the electrical resistance in the variable resistor, which then sends the right information to your gauge on the dashboard. This is what gives you an accurate reading of your fuel level.

Causes of Fuel Gauge Not Working Correctly

A faulty fuel sending unit is one of the most common reasons for a fuel gauge to give incorrect readings. This essential component is responsible for measuring the fuel level in the tank and conveying this information to the fuel gauge located on your car’s dashboard.

Other potential culprits for wrong readings include a blown fuse, damaged wiring connecting the gauge and fuel sender, or even a malfunctioning fuel gauge itself.

Let’s discuss the main causes of the fuel gauge not working correctly. 

1) Faulty Fuel Sending Unit

 A faulty fuel sending unit is one of the major causes of the gas gauge giving wrong readings. The fuel sending unit is responsible for detecting the fuel level and transmitting this data to either the engine control module (ECM) or the gauge on the dashboard.

Since it contains several moving components involved, wear and disconnections can occur over time. When floats become disconnected, the gauge might constantly show an empty reading, while a bad resistor may lead to erratic readings.

2) Faulty Instrument Cluster

In the latest models, the fuel gauge is installed into the instrument cluster. Unfortunately, this means that the gas gauge and the instrument cluster are interconnected within one unit.

Consequently, if there is something wrong with the instrument cluster, it may also lead to an issue with the gas gauge. Regrettably, repairing this integrated system tends to be one of the costly actions.

3) Faulty Fuse

In addition to the electrical connections, the fuel gauge system contains a fuse. This fuse is typically installed in the fuse box on the driver’s side or beneath the steering column. Some vehicle models may also have a fuse box beneath the hood.

Inspecting the fuse is a straightforward process that only takes a few minutes. To identify the specific fuse responsible for the gas gauge, you may refer to the fuse map in your vehicle’s service manual.

It’s worth noting that the latest vehicles usually integrate the fuel gauge with the instrument cluster, which may not have a separate fuse, but it’s still a good idea to check if you’re experiencing issues.

4) Circuit Issues

The fuel gauge relies on electrical power. Therefore, the electrical wires and circuits connected to the gauge must work efficiently.

Any issues within this system can result in insufficient voltage for accurate gauge readings. Sometimes, the problem may arise from a disrupted ground connection.

But loose connections or corrosion may cause problems as well. These issues are most often observed in the connections to the fuel pump module, primarily due to its exposure to the elements.

5) Broken Gas Gauge

Although less common, an internal circuit malfunction within the fuel gauge can also be a potential culprit. When this occurs, the gauge needle may provide readings at unpredictable levels.

If you observe the gauge needle positioned between the halfway mark and empty or full, it may indicate a circuit failure in a specific region. Conversely, if your gauge needle remains stuck at either empty or full point, it indicates a short circuit.

In such cases, it’s unlikely that the gauge will function properly again without replacement.

How to Test the Fuel Gauge

Follow the following steps to test the fuel gauge:

1) Self-Test Instrument Cluster

Consult your vehicle’s manual to discover if your instrument cluster offers a self-test procedure. This process varies depending on the make and model, and it might involve actions such as toggling the headlights on and off while simultaneously pressing a button or switching the ignition.

While performing this test, observe the fuel gauge as it completes a full sweep across its range. If it fails to do so, there may be an issue with the instrument cluster or the fuel gauge.

2) Test Fuel Sending Unit

Use a multimeter to assess the resistance of the fuel sending unit when the fuel tank is full. Consult your vehicle’s manual to determine whether your specific vehicle has minimal or maximum resistance when the tank is full.

If the multimeter reading shows a significant deviation by numerous ohms from the expected value, this indicates an issue with the sending unit. Before considering a complete replacement of the unit, it is recommended to try using a fuel system cleaner to observe if it can fix the problem.

3) Check Electrical Wires

Although inspecting all the electrical wires can be somewhat time-consuming, it’s a necessary step. Begin by examining the wiring harness connected to the fuel tank. Additionally, pay attention to the ground connections, as they may corrode over time due to exposure to salt, snow, and rain.

If you come across any corrosion, disconnect that particular connection and thoroughly clean it. Ensure it is reattached to its proper position. In the event of a damaged wire, it must be replaced.

Another diagnostic option is to measure the resistance of the wiring from the gauge using a multimeter and then compare these readings to those obtained at the fuel sending unit. If there’s a noticeable difference in these readings, it’s highly possible that there’s a short or open circuit that requires attention.

4) Inspect Fuse

If you’ve been experiencing erratic gauge behavior, consider inspecting the fuses related to your gauge or instrument panel.

Start by removing the fuse box cover and examining the fuses to see if any of them become faulty. If you find any faulty fuses, replace them and reattach the fuse box cover.

Before proceeding further, assess whether it’s easier to access the fuel gauge or the fuel sending unit in your vehicle. Prioritizing the more accessible component for inspection could save you valuable time and effort if it turns out to be the source of the issue.

5) Check the Gauge

In the case of old vehicle models, the fuel gauge typically has two terminals. One terminal connects to the wire coming from the fuel sending unit, while the other terminal receives power whenever the ignition is on.

To check for continuity, test the connection between the sending terminal and the one at the fuel tank. If you find no continuity, it means your wire is broken, and you need to repair it.

In the case of newer vehicles, testing the fuel gauge can be quite challenging, especially if it’s installed into the instrument cluster. In this case, you will need to disassemble the whole cluster to access the gauge. Therefore, it’s advisable to start by carefully inspecting the sending unit and wires before attempting more complex diagnostic procedures.

Fuel Gauge Replacement Cost

The repair cost of a malfunctioning fuel gauge may vary according to the underlying. The average fixing of a faulty fuel gauge is from $10 to $820.

The most budget-friendly solution is often to change a blown fuse, a straightforward DIY task that can cost as little as $10. In contrast, if your fuel gauge itself is broken, the expense typically falls between $40 and $220 if you can handle the installation yourself. But if you require a mechanic’s expertise for the installation, you may incur an additional cost of $80 to $240.

How do you reset the fuel gauge?

If your fuel gauge is not working correctly, it is typically indicative of a software or electronic fault related to the fuel gauge system.

The primary solution for addressing a wrong fuel gauge reading involves performing a reset. While manufacturers often provide specific reset procedures in the owner’s manual. However, these methods tend to be fairly the same across many vehicle models, including Mercedes models, which are no exception.

Follow the following steps to reset your fuel gauge:

• Start by turning the ignition key to the “ON” position.
• Locate and push the “Trip/Odo” button to switch the Odometer display to “ODO” mode.
• Switch off the ignition key.
• Now, press and hold the “Trip/Odo” button again. While holding it, again switch on the ignition switch. Keep holding the “Trip/Odo” button for approximately two seconds, then release it. Afterward, press it three or four more times and hold it for about three to five seconds until you see leveling data displayed on the Odometer. Now, release the “Trip/Odo” button.
• Again, press and hold the “Trip/Odo” button until the Odometer shows “1,” indicating the reset process has started.
• Finally, when the Odometer reading returns to its normal state, release the “Trip/Odo” button. This signifies the completion of the reset procedure.

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