Since you have described a push button switch that is pushed by the door, not a rocker switch located near
the door, the suggestions of a propane shut off and battery cut off are pretty much out.
You said the switch is toast, I'd pull it out and check the wiring for any labels, which is often done to wiring harness make ups. Also, it will allow you to use a meter to see if the wires have current and under what circumstances. If they become 'hot' when the ignition is on, etc. It will also allow you to touch the two ends together so you can see if it activates something. If the switch only has one wire, the case in many auto door switches, it closes the circuit by connecting to ground.