3 Symptoms Of A Bad Fuel Gauge Sender (& Replacement Cost)

It may seem obvious that having an operating gas gauge inside your car is important. It tells you how much fuel is left in the tank and alerts you when it’s time for a fill-up.

The fuel gauge sender relays this information, but it’s not immune to malfunctions. If your vehicle has a defective fuel gauge transmitter, data could not be sent correctly.

A bad fuel gauge can lead to erratic behavior and readings that are too low or full. If the fuel gauge starts acting up it may be due to a malfunctioning sending unit. 

Each of the symptoms that indicate a defective fuel sender unit are discussed. This article will also address the replacement cost for a fuel gauge sending unit, and the exact location and operation of this vital component. 

Bad Fuel Gauge Sending Unit Symptoms

1. Erratic Gage Behavior

It should not make sudden changes to the fuel gauge or act erratically. When it’s operating correctly, the fuel gauge is going to consistently move toward empty until you refill the tank.

You might observe a change in behavior if the fuel gauge transmitter fails. You might notice a sudden shift in the gauge's position, or an incorrect reading. 

The tank might be three quarters full at one time, but it could read empty in the next. A bad fuel gauge transmitter is usually the culprit. 

Similar: Is the Fuel Gauge not working or is it inaccurate?

2. Gauge is stuck at empty

It’s also possible for the fuel tank to read empty even when it’s not. If you’ve put fuel into the tank, but the gauge doesn’t move, this is a clear sign that the sending unit has failed.

If the float gets detached from the arm or breaks, the gauge can malfunction. It will display an empty tank if there is nothing to read. A faulty resistor can also lead to this problem. 

3. Get your Gauge stuck at Full 

It is not common but it can happen. If your fuel gauge is not working properly, it could be an indication of a poor resistor.

You get the tank indicator because the resistor is sending the wrong signal. However, if the resistor isn’t to blame, it’s possible that the sender is the culprit instead. 

Fuel Gauge Sender Location

Your vehicle's fuel tank houses the fuel gauge sender. The fuel pump will have it attached.

It has a base with a rod and floating float that will allow you to locate the sender. It is hollow and light in appearance. It’s meant to sit on the fuel surface and it doesn’t sink. Attached to the base, it contains an insulated rod. Rheostat Meter to register how much fuel is in your car’s tank. 

A Fuel Gauge Sender's Function 

When you add gas to the tank, the floating part sits above it. The rod that is attached to the float also moves as the float rises. To determine the fuel level in the tank, the coil attached to the rod measures resistance. Low floats allow for the current to flow quickly. Higher floats will result in a higher resistance, which causes the electric current to travel slower.

The resistance measurement of the sender is measured by the fuel gauge. Lower resistance means that the fuel gauge is closer to empty (E), on the dashboard. The fuel tank may be full if the resistance is at the very top of the spectrum (F). The resistance at the top of the spectrum is F. However, the entire range between full and empty marks can be measured so you always know how much fuel there actually are. 

Fuel Gauge Sender Replacement Cost

A fuel gauge sender replacement cost is approximately $800 to $1,000. While labor is approximately $150-200, parts are $650-$800.

The cost of replacing the fuel gauge sender will vary depending on which car you have and how complicated it is to install. You can repair the fuel gauge sender yourself if you have the tools and are mechanically skilled.

It is possible to drive a car with a defective fuel gauge sender. However, you won’t have an accurate reading showing how much fuel is in the gas tank. Some people choose to use the trip meter to measure how much fuel is left, but this method isn’t reliable. Although it might seem like you could just carry your fuel tank in your trunk, this is extremely dangerous due to the potential for fire and fume exposure.