It's a must-have for any toolbox—but there's a learning curve involved. Learn how to use a multimeter for all of your electrical testing needs.

If I were to test our fictitious 200 K ohm resistor with this particular meter, I would set the scale at 200 K ohms. However, it’s purely a coincidence that my meter has a setting for 200 K ohms.

The black probe connects to your multimeter's "COM" terminal. The red probe goes in the terminal labeled volts (V) and ohms (omega symbol). Turn the multimeter dial to the DC voltage position.

If your gauge is good, check the ground at the sender with your multimeter set to ohms. Look for a “no resistance” reading between the ground on the sender and your boat’s battery ground.