LG LMVM2277ST Product Training Manual page 59

Door Interlock Switches
PRIMARY and SECONDARY SWITCHES
Disconnect the wire lead from the switch.
Connect an ohmmeter to the COM (common) and NO
(normally open) terminals of the switch.
With the door open, the meter should indicate an open
circuit.
Closing the door should indicate a closed circuit.
(See chart, couple of slides later.)
T-20
LMVM2277ST
59