Power Locks: Description and Operation

When a Door Lock and Side Window Switch is activated in the Power Door Lock System, all doors lock or unlock in unison. Each lock can also be operated manually from the locking knob. The locks are operated by reversible actuators that receive voltage from the Door Lock Relay. The Door Lock Relay turns the actuators on by applying voltage to one of that terminals and ground to the other terminal. To reverse the actuators, the polarity to the terminals must be reversed.

When either Door Lock and Side Window Switch is moved to the Lock position, it completes a circuit to the coil of the Door Lock Relay. The Door Lock Relay is energized. Its contact for the Lock Relay closes and is connected to battery voltage through CKT 540, which is the voltage feed for driving the actuators.

Voltage is then applied to CKT 295 and to the Door Lock Actuators, which are grounded by CKT 294 from the other terminal of the motor through the contact for the Unlock Relay. The actuator in each door runs to operate the door lock. When the Door Lock and Side Window Switch is released, the Lock Relay contact closes to ground again and the actuators turn off.

A similar action occurs with the Door Lock Relay when it is energized by either of the Door Lock Switches closing to the Unlock position. Now CKT 294 to the actuators carries battery voltage and CKT 295 is grounded. The polarity of the voltage to the actuators has reversed. The actuators 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, a circuit breaker in each actuator will open to protect against damage. The circuit breaker resets only after voltage is removed from the actuator.