* Switch Activation: When you press the lock or unlock button on the key fob, the driver's door switch, or the power door lock switch on the center console, it sends an electrical signal.
* Body Control Module (BCM): This electronic control unit receives the signal from the switch. The BCM interprets the command and sends a signal to the appropriate actuators.
* Door Lock Actuators: Each door (and sometimes the trunk/hatch) has an electric actuator. This is a small motor that is responsible for physically moving the locking mechanism. When the BCM sends a signal, the motor within the actuator rotates, extending or retracting a rod or cable that engages or disengages the locking mechanism.
* Locking Mechanism: This is the mechanical part of the door lock that actually secures the door. The actuator's movement either pushes a bolt into the door frame (locking) or retracts it (unlocking).
* Power Supply: The entire system runs on the vehicle's 12-volt electrical system. A faulty fuse or wiring problem can prevent the system from functioning.
Troubleshooting a Malfunctioning System: If your Ford Tempo's power door locks aren't working, potential problems include:
* Blown fuse: Check the fuse box for a blown fuse related to the power door locks.
* Faulty switch: A malfunctioning switch may need replacement.
* Wiring issues: Damaged or corroded wiring between the switches, BCM, and actuators can interrupt the electrical signal.
* Bad BCM: The Body Control Module itself can fail, requiring replacement. This is usually the last thing checked due to the expense of replacing the BCM.
* Failing actuator: The motor within the actuator may be worn out, jammed, or otherwise malfunctioning. This is a common cause of individual door lock failure.
* Vacuum system (on some models): Some older models used a vacuum system instead of electric actuators; leaks in the vacuum lines would lead to malfunction.
To diagnose the specific problem, you'll likely need to use a multimeter to check for power and continuity at various points in the system. A repair manual specific to your year and model Ford Tempo will be invaluable in troubleshooting.
