TM 9-2350-277-34THEORY OF OPERATION — Continued 0003 00The variable speed fan drive system is designed to modulate the cooling fan speed to maintain relatively constant coolanttemperatures despite vehicle load or ambient temperature. The cooling fan speed is controlled by the fan drive assembly. Thefan drive assembly is driven by the engine crankshaft through a splined coupling. The fan drive assembly contains amulti-plate clutch pack which regulates the fan drive output speed. The thermostatic control valve senses engine coolanttemperature and regulates the hydraulic pressure to the fan drive assembly clutch pack. The higher the coolant temperature,the higher the hydraulic pressure which will result in less clutch slip and higher fan speed.The surge tank acts as an overflow tank to keep the cooling system from overpressurizing. It also removes air from the enginecoolant. There is a low coolant level transmitter to signal the operator if more coolant is needed.ENGINE AIR SYSTEMThe engine air system allows air to enter the engine. The air cleaner cleans air that enters the engine. Dust is drawn outthrough a scavenge outlet. Air is filtered through a reusable filter element before delivery to the engine. An air filter indicatorshows when the element is clogged and needs cleaning or replacing. After being filtered, the air moves through theturbocharger and into the engine cylinders.AUXILIARY AUTOMOTIVE SYSTEMSThe auxiliary automotive systems include driver controls, fuel cells, personnel heater, and bilge pumps. Also there is a crewventilation system, and fire suppression system.DRIVER CONTROLSThe driver controls regulate the engine, transmission, and steering braking systems of the carrier.The fuel shutoff control is used to stop the supply of fuel to the fuel pump. To start the engine, the driver must open the valve.The throttle linkages are used to control the engine speed. The gear selector allows the driver to choose the proper gear for thecarrier. The steering system controls the carrier direction. The steering control consists of a steering yoke and linkageconnected to the transmission.The brake system allows the driver to stop a moving carrier and hold the carrier in position. The braking system consists ofthe service brake and the parking brake. The service brakes are hydraulic and applied by pedal. The parking brakemechanically locks the transmission to prevent carrier movement. Also, the system has levers, rods, shafts, and linkagesconnecting to the transmission brake shaft.FUEL TANKSDiesel fuel is stored in two separate fuel tanks. They are located on the back of the carrier hull. The fuel is drawn from thefuel tanks through the primary fuel filter by the fuel pump. The fuel then flows through the secondary fuel filter to theinjectors. The injectors regulate the amount of fuel that enters the engine.PERSONNEL HEATERThe personnel heater system provides heat inside the carrier. Major parts are the combination combustion chamber/heatexchanger, blowers, a fuel pump, and an electrical control and safety system. The heater operates using diesel fuel drawnfrom the fuel tanks. Fuel is delivered to the combustion chamber from the fuel pump. Outside air is drawn into thecombustion chamber by one of the blowers. A blower draws air from the crew compartment into the combustion chamber.The air is warmed by heat from the combustion process and then returned to the crew compartment.BILGE PUMPSTwo electrically driven bilge pumps remove water and other liquids from the hull. Water enters the pumps through a screenedinlet. The pumps force water out of the carrier through outlet tubes. The bilge pumps are controlled by a switch on thedriver’s instrument panel.0003 00-2
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