Fig. 1: The infinite reading on this multimeter indicates
that the circuit is open
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This test already assumes the existence of an open in the circuit and it
is used to help locate the open portion.
- Isolate the circuit from power and ground.
- Connect the self-powered test light or ohmmeter ground clip to the ground
side of the circuit and probe sections of the circuit sequentially.
- If the light is out or there is infinite resistance, the open is between
the probe and the circuit ground.
- If the light is on or the meter shows continuity, the open is between
the probe and the end of the circuit toward the power source.