A circuit consists of the power supply, switch, relay, load, ground, etc. There are various methods to check a circuit including an overall check, voltage check, short circuit check and continuity check.
Continuity Check:
Continuity Check
a. When the switch is in the OFF position, the self power test light should come on or the ohmmeter should read 0 Ohm only when the terminals 1 and 2 are interconnected.
b. When the switch is in the ON position, the self power test light should come on or the ohmmeter should read 0 Ohm only when the terminals 3 and 4 are interconnected.