Connect the Clamp: Attach the alligator clip at the end of the wire to a clean, unpainted metal part of the vehicle’s chassis (ground) or the negative $(-)$ terminal of the battery.

Test the Tester: Touch the sharp tip of the pen directly to the positive $(+)$ terminal of the battery. If the bulb inside the handle lights up, your tester is working properly and you have a good ground connection.

Test the Circuit/Fuse: * For Fuses: Touch the probe tip to the small exposed metal pads on top of a fuse. If it lights up on one side but not the other, the fuse is blown.

• For Wires/Sockets: Gently touch the probe to the wire terminal or connector you want to check. If the light turns on, power is reaching that point.