Match the wire gauge (AWG) to the load: 16 AWG: Lights/small electronics (<10A). 14 AWG: Power tools (10–15A). 12 AWG: Heavy-duty equipment (15–20A)

Unplug devices, press the reset button, and check for internal fuse failure (replace if needed).

Ensure the circuit is unpowered, probes are in the Ω (ohms) ports, and the component is isolated (not in-circuit).