A car's fuel gauge is located in the instrument panel and is made up of a sender and a gauge. The sender measures the amount of fuel in the tank and then proceeds to "send" the data to the gauge, which is the part that actually tells the driver how much gas is in the tank. There are several reasons that a fuel gauge may give a false reading or stop working altogether. Luckily, there is a way to test a fuel gauge if you notice a problem.
Remove the instrument panel with the fuel gauge. Release any plastic clips that may hold it in place. Also, press any plastic tabs inward to release them.
Examine the now-exposed wiring behind the fuel gauge and instrument panel.
Remove any dirt or debris from the wires. Focus especially on the connection points. Debris can interfere with the function of the wires. Use a dry rag or brush to clean the wires.
Replace the instrument panel by reversing the steps you took for its removal.
Locate the sensor in your car. Remove the back seat or the boot carpeting. Consult your service/owner's manual to determine exactly where your sensor is located.
Examine the wiring connected to the sensor and the fuel tanks. Remove any debris with a rag or brush. Pay close attention to the connections between the devices.
Replace the back seat or boot carpeting depending on which you needed to remove.
Turn on the car and monitor the fuel gauge needle. If the needle moves, you have solved the problem. If there is no movement of the needle, continue on to the next step to check the fuse.
Determine if you need to check the fuses. Turn the car on and off several times and monitor the fuel gauge needle. If the needle does not move, proceed to the next steps on checking the fuse connected with your fuel gauge.
Lift the bonnet of your car or open the fuel box in your dashboard. Consult your service/owner's manual to determine where your fuses are located.
Consult your service/owner's manual to determine which fuse is connected with your fuel gauge system.
Replace the bad fuse. Pull the old fuse out of its slot in the fuse box. Insert the new, working fuse in the same slot. The new fuse needs to have the same amp rating as the old fuse. See the numbers on the fuses to determine the amp rating.
Close the bonnet of your car or the fuse box depending on which you had to open. Start the car. If the needle moves, the bad fuse was the only problem. If the needle doesn't move, continue to the next section.
Test the wiring that runs between the ignition switch and the fuel gauge. Attach jump leads to the car. Clamp one cable on to the fuel gauge's terminal and the other cable to the ignition switch. Turn the car on and monitor the fuel gauge needle. If there is movement of the needle, you will need to replace the wiring that connects the ignition switch and the fuel gauge.
Test the fuel gauge grounding wire. Clamp one jump lead to fuel gauge's grounding cable. Clamp the other cable to the frame of the car. Turn the car on and monitor the fuel gauge's needle. If there is movement of the needle, you will need to install a new fuel gauge grounding wire.
Test the grounding wire of the sending unit. Attach one jump lead to the grounding wire of the sender unit. Attach the other jump lead to the sender unit. Turn on the car and monitor the needle of the fuel gauge. If there is movement of the needle, you will need to replace the grounding wire of the sender unit.
Test the fuel gauge itself. Unplug the wire between the sender and the fuel gauge. Turn on the car and monitor the fuel gauge needle. If the needle sits at the "E" for empty, this means that you have a bad fuel gauge. If the needle rises to "F" for full, this means that you have a problem with the sender.