Regan Brown
There are several reasons why your car's fuel gauge may not be reading correctly. The sending unit in your fuel tank transmits the amount of fuel to the gauge on your dashboard. If there is a problem with the sending unit, you can get an incorrect high or low reading. A faulty gauge itself can also cause irregular readings. A bad fuse can also cause the fuel gauge to read incorrectly.
What You'll Learn
Float sticking
The float arm measures resistance in the tank — zero ohms if the tank is empty and somewhere around 60 ohms if the tank is full. That resistance is then converted to a reading on the dashboard gauge via the sending unit.
If you suspect that your fuel gauge is not reading correctly, it's best to have it checked by a professional. They can diagnose the problem and recommend the best course of action.
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Faulty gauge
A faulty gauge is a common reason for an incorrect fuel gauge reading. The sending unit in your fuel tank transmits the amount of fuel to the gauge on your dashboard. If there is a problem with the sending unit, you can get an incorrect high or low reading.
The sender itself can also be the culprit, and would have to be replaced. The float arm measures resistance in the tank — zero ohms if the tank is empty and around 60 ohms if the tank is full. That resistance is then converted to a reading on the dashboard gauge via the sending unit.
Sometimes, a faulty fuse can cause the fuel gauge to read incorrectly. One clue that this is the problem is when other elements nearby on the dashboard also appear to be incorrect.
The gauge can also swing back and forth between full and empty with no rhyme or reason. This is usually a result of the float “sticking” in place and then being jolted back into motion by the movement of the car.
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Broken gauge
A broken fuel gauge is a common problem that can be caused by a faulty sending unit, a faulty fuse, or a faulty gauge itself.
The sending unit is located inside the fuel tank and transmits the amount of fuel to the gauge on your dashboard. If there is a problem with the sending unit, you can get an incorrect high or low reading.
A faulty fuse can also cause the fuel gauge to read incorrectly. One clue that this is the problem is when other elements nearby on the dashboard also appear to be incorrect.
The gauge itself can also be faulty, causing it to swing back and forth between full and empty with no rhyme or reason. This can be caused by the float "sticking" in place and then being jolted back into motion by the movement of the car.
If you suspect that your fuel gauge is broken, it is best to have it checked by a mechanic to determine the cause and get it fixed.
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Sender unit
The fuel tank has a sending unit in it that transmits the amount of fuel to the gauge on your dashboard. If there is a problem with the sending unit, you can get an incorrect high or low reading. The sending unit uses a float, not unlike the float you’ve probably seen inside toilet tanks, with an arm attached to the main mechanism. The float arm measures resistance in the tank — zero ohms if the tank is empty and somewhere around 60 ohms if the tank is full. That resistance is then converted to a reading on the dashboard gauge via the sending unit.
Occasionally, the sender itself is the culprit and would have to be replaced. Depending on the age of the car, your sending unit will have one or two wires emanating from it.
Sometimes, a bad fuse can cause the fuel gauge to read incorrectly. One clue that this is the problem is when other elements nearby on the dashboard also appear to be incorrect. Most often, the oil gauge will be affected by a faulty fuse as well. Whether it’s a digital fuel gauge reading incorrectly or a conventional analog one, your mechanic can track down the cause with a bit of detective work.
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Bad fuse
A faulty fuse can cause the fuel gauge to read incorrectly. One clue that this is the problem is when other elements nearby on the dashboard also appear to be incorrect. Most often, the oil gauge will be affected by a faulty fuse as well. Whether it’s a digital fuel gauge reading incorrectly or a conventional analog one, your mechanic can track down the cause with a bit of detective work. Sometimes, they’ll perform an instrument cluster self-test first. This initiates a sort of reset process with certain dashboard instruments. If the fuel gauge doesn’t move during this process, the issue is located somewhere around the dash with the gauge itself.
The fuel tank has a sending unit in it that transmits the amount of fuel to the gauge on your dashboard. If there is a problem with the sending unit, you can get an incorrect high or low reading. Depending on the age of the car or truck, your sending unit will have one or two wires emanating from it. The float arm measures resistance in the tank — zero ohms if the tank is empty and somewhere around 60 ohms if the tank is full. That resistance is then converted to a reading on the dashboard gauge via the sending unit. Occasionally, the sender itself is the culprit. In that case, it would have to be replaced.
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Frequently asked questions
There are several typical reasons why the fuel gauge in your car, truck, or van isn’t working properly. Your fuel tank has a sending unit in it that transmits the amount of fuel to the gauge on your dashboard. If there is a problem with the sending unit, you can get an incorrect high or low reading.
The gauge swings back and forth between full and empty with no rhyme or reason. This is usually a result of the float “sticking” in place and then being jolted back into motion by the movement of the car. It can cause irregular readings. Another cause could be a faulty gauge itself.
Depending on what’s causing it, your mechanic can usually fix the issue fairly easily and quickly.
Have you ever filled up your car’s tank at a gas station, only to have the fuel gauge on your dashboard read nearly empty or one-quarter full a few minutes later? Or you drive for a few hours, but the gauge is still reading as if your tank is full? Maybe the gauge oscillates between the two randomly.
A wrong fuel gauge reading will mess up those figures. Or you’ll be constantly running to the filling station just in case your fuel is low and you don’t know it to prevent emergencies.
