Door Locks: Description and Operation

When a Door Lock Switch is activated in the Power Door Lock System, all of the doors lock or unlock in unison. Each lock can also be operated manually from the locking knob. The locks are operated by reversible motors that receive voltage from two relays in the Door Lock Relay Assembly. These relays operate to turn the motors on by applying voltage to one of the terminals and ground to the other terminal.
When either Door Lock Switch is moved to the LOCK position, it completes the circuit to the coil in the Door Lock Relay Assembly. The Door Lock Relay is energized. Its contact for the Lock Relay closes and it is connected to battery voltage through the ORN/BLK wire.
Voltage is then applied to the GRY wire and to the Door Lock Motors, which are grounded by the TAN wire from the other terminal of the motor through the contact for the Unlock Relay. The motor in each door runs to operate the door locks. When the Door Lock Switch is released, the Lock Relay contact closes to ground again and the motors turn off.
A similar action occurs with the Unlock Relay when it is energized by either of the Door Lock Switches closing to the UNLOCK position. The TAN wires to the motors carry battery voltage and the GRY wires are grounded. The polarity of the voltage to the motors reverses. The motors run in the opposite direction to unlock the doors.
The Door Lock Switches are usually closed for just a moment. If they are held closed, an electronic circuit breaker in each motor will open to protect against damage. The circuit breakers have positive temperature coefficients (PTC) and reset automatically when voltage is removed from the motor.