1.18.2. Battery/Starting Circuit.

TM 5-3895-373-20 1.18.2. Battery/Starting Circuit. The engine starting circuit is controlled by the fuel shutoff solenoid and start relay. The fuel shutoff solenoid is energized through contacts in the high temperature shutdown sensor and the DCA engine test switch. The start relay is energized through relays controlled by the control handles. Electrical power at 12 VDC is supplied from CB1 to the normally closed contacts of the high temperature shutdown sensor. When engine temperature is below 220°F (105°C), the 12 VDC passes through the temperature shutdown sensor to the DCA engine test switch. The DCA ENGINE CRANK switch spring return the closed position and is only used when testing the, engine. The electrical power passes through the ENGINE CRANK switch to energize the fuel shutoff solenoid. When engine temperature is above 220°F (1050C), the high temperature shutdown sensor contacts open and prevent the fuel shutoff solenoid from being energized. This cuts off fuel to the engine and prevents the engine from being started. In emergencies, the high temperature manual override button may be pushed and held to allow starting the engine. The override button supplies power to the engine fuel shutoff solenoid from CBI as long as the button is held. This bypasses the engine high temperature shutdown sensor. Electrical power from CB1 is also routed to both control handles. With the left control handle in the center detent position, the control handle sends a 12 VDC signal to the contacts of relay R3. With the right control handle in the center detent position, the control handle passes a 12 VDC signal which energizes relay R3. This closes the contacts of relay R4. With relay R4 energized, the start position of the ignition switch sends 12 VDC through the contacts of relay R4. This signal energizes the coil of the start relay. The batteries send 24 VDC through the contacts of the start relay, engaging the starter solenoid and turning the starter. Releasing the ignition switch from the "START" position removes the voltage from the coil of the start relay and disengages the starter. 1-24