Mercury Repair Questions? Ask a Mechanic for Answers ASAP
If you mean the door ajar light comes on with the doors closed try this:
The security system and door locks all tie into the door ajar switches.
Let me know if it still does it
Anti-Theft- Perimeter Alarm System
The perimeter anti-theft system provides for vehicle security through an audible and visual notification if the vehicle's exterior is invaded without the system being shut off. The system self-arms when the doors, liftgate and hood are closed and the key is OFF. Any open door, hood or liftgate will prevent the system from arming. The hood ajar switch, door ajar switches and liftgate ajar switch cause these circuits to register as normally closed circuits. The vehicle security module monitors the status of the hood ajar, door ajar and liftgate ajar switches. If these circuits indicate an open entry point, the switch opens the circuit to the vehicle security module, which energizes the horn and autolamp relays (causing the horn to sound and the lights to flash). The vehicle security module turns off the anti-theft system when it receives a command through the keyless entry keypad, remote keyless entry (RKE) transmitter, or anti-theft alarm inhibit switch.