I do not know what meter you have, but, most meters run on a 9 volt battery. To check resistance the switch should be unhooked, but definitely no power to it. Hook the meter up and then cycle the switch. It should go from low resistance(less than .3 ohms) to infinity resistance(---- might display, OC, or OL). Most safety switches are low resistance, but, some have a specific resistance that the module(OPC in this case) has the see. In automotive air bags have to have a certain resistance to prevent a short(low resistance) failing to detect an issue within system. This is done to prevent people from disabling them. Your reading sound like a backfeed thru the system(or voltage still present, but, the meter is draining it). I hope this helps as electronics are hard to understand and even harder to diagnose over the phone(Been in the over the phone tech support role).