Operation CHARM: Car repair manuals for everyone.

Power Locks: Description and Operation

CIRCUIT OPERATION
The Automatic Door Lock feature is controlled by the Chime Module. The Chime Module will send a 400 ms battery voltage signal to the coil of the Door Lock Relay once per Ignition cycle when two conditions are present: all doors are closed and the Gear Selector is moved out of "Park" or "Neutral."

Door Locks
When a Door Lock Switch is activated in the Power Door Locks 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 motors that receive voltage from two relays in the Power Door Lock Relay. These relays operate to turn the motors on by applying a voltage to one of the terminals and a ground to the other terminal. To reverse the motors, the polarity to the terminals must be reversed.

When either Door Lock Switch is moved to the "LOCK" position, it completes a circuit to the coil of the Power Door Lock Relay. The Power Door Lock Relay is energized. Its contact for the Lock Relay closes and is connected to battery voltage through CKT 60, which is the voltage feed for driving the motors.

Voltage is then applied to CKT 295 and to the Door Lock Motors, which are grounded by CKT 294 from the other terminal of the motor through the contact for the Unlock Relay. The motor in each door runs to operate the door lock. 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 Power Door Lock Relay when it is energized by either of the Door Lock Switches closing to the "UNLOCK" position. Now CKT 294 to the motors carries battery voltage and CKT 295 is grounded. The polarity of the voltage to the motors has reversed. 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, a circuit breaker in each motor will open to protect against damage. The circuit breaker resets only after voltage is removed from the motor.