MaxQ said:
(1) Check the carpet on the passenger side, make sure it's not soaked. Sure sign of a leaking heater core if it is. There are also a few hoses on the backside of the motor that can leak and if it drips on the engine it will evaporate almost immediately. You'll smell that for sure.
(2) The lock on the passenger side door may be out of adjustment, either the pin or the lock inside the door itself, both can be adjusted by loosening the bolts and moving it. Does the door sound loose at all? I beleive there is a way to disable the switch on that side, but you'd have to take the switch apart. It's on the rear side of the door sill on the bottom part, on the car itself, not the door.