How do you tell if gas gauge is bad?

Answer 1

If it reads full and you run out of gas, haha Seriously, though, there are really two main reasons why your gauge would be bad. The first, and most common is a bad float/sending unit. The float/sending unit sits in your gas tank, and sends a signal down a wire to your gauge The signal varies in voltage based on how full or empty your tank is. Most of the time, this can only be replaced with a whole module (comes with float, sender [the part that transmits the signal], wiring harness, and fuel pump) at between $150-300, depending on the vehicle. This is all assuming that your vehicle is pretty current. If it is an antique, or collectible it may have a separate sensor that sits in the tank. This is much easier and cheaper to replace, but it may be harder to locate the part for purchase.