Door Locks: Description and Operation
CIRCUIT OPERATIONWhen a power Door Lock Switch is pushed, all of the doors will lock or unlock. Each lock can also be operated manually. The locks are operated by two reversible motors that receive voltage from two relays in the Door Lock Relay. These relays operate to turn the motors "ON" by applying battery voltage to one motor terminal and ground to the other terminal.
When either Door Lock Switch is moved to the "LOCK" position, it completes the circuit to the lock coil in the Door Lock Relay. The Lock Relay is energized. The contact for the Lock Relay closes and battery voltage is applied through CKT 60 to the closed contact.
Voltage is then applied to CKT 295 and 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 locks. When the Door Lock Switch is released, the Lock Relay contact returns to ground 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. Now CKT 294 to the motors supplies battery voltage and CKT 295 is grounded. The polarity of the motors has reversed and the motors run in the opposite direction to unlock the doors.
The Door Lock Switches are usually closed for just a moment. If the Door Lock Switches are held closed, a circuit breaker in each motor will open to protect against damage. The circuit breaker will not reset until voltage has been removed from the motor.