This makes sense to me and aligns with what I had researched from your initial reply, but what I don't understand is that when the wall plug is removed from the circuit, the motion sensor works fine. When the 12v is added (either ground or positive), the PIR pull down resistor is immediately required. why would it work in one scenario and not in the other since the PIR is not being modified. Is connecting it to the ground of the house via the wall plug affecting it?