BEARING-THR-YM 3777409 - Caterpillar

Illustration 1 g00743068
ECM Inputs
Keyswitch
The key start switch is also used as an input signal to the MSS. The input from the key switch is used to determine when the machine is on. Battery voltage is connected to this input through the ON and START positions of the keyswitch. When the machine is operating and the alternator is charging, the voltage on this input will be 14.1 - 15.1 Volts for a 12 Volt system and 27.6 - 29.6 Volts for a 24 Volt system. When the machine is not running, the voltage on this input will be approximately 12 Volts for a 12 Volt system and approximately 24 Volts for a 24 Volt system.Alternator "R Terminal"
The input for the hour meter is connected to the terminal R on the alternator. The signal from the terminal R is a square wave when the engine is running. The frequency is proportional to engine RPM. The frequency will be within the range of 0 to 2 kHz. This is pin 26 of the Machine Security System ECM.ECM Outputs
Status Indicator
The status indicator displays status of the system. The status indicator has three connections. One of the three connections is for a ground. Another connection is for the red LED. The third connection is for the green LED. Low Voltage Indication of the Electronic Control Module's Internal Backup Battery
The internal backup battery is used to maintain the list of keys and the Bypass schedule when the machine is turned off. The battery should last 10 years or more. The internal backup battery is NOT serviceable. The MSS ECM monitors the battery voltage. The ECM notifies the operator of a low voltage condition by alternately blinking the red LED and green LED for ten minutes. The MSS is permanently disarmed when the low voltage condition is detected.Output Drivers
Two output drivers are available to control relays or solenoids on the machine. Unless a valid "key ID" has been identified by the system, the drivers will remain without power. The drivers are rated at 3 amperes.