TM 9-2350-277-20-1
THEORY OF OPERATION — Continued
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FIRE EXTINGUISHER SYSTEM
The fire extinguisher system consists of two CO2 (Carbon Dioxide) cylinders, one fixed and one portable. Carbon Dioxide
can put out fires quickly and effectively. The fixed cylinder only extinguishes fires in the power plant compartment. It is
located behind the driver and is actuated manually by a handle/knob on the cylinder or by an external handle connected to the
cylinder by a cable. The portable fire extinguisher is located in the crew compartment and is manually discharged.
SUSPENSION SYSTEM
The suspension system supports the carrier and delivers engine power to the road. It allows the carrier to maneuver and be
stable. Suspension system parts are the drive sprockets, tracks, idler wheels, track tension adjuster, road wheels, and support
arms. Also, there are torsion bars and shock absorbers.
The drive sprockets drive the tracks. They are powered by left and right final drives from the transmission. The tracks consist
of two flexible chains of track shoes. The tracks ride on the drive sprockets and are guided by idler wheels. The idler wheels
can be adjusted to maintain correct track tension.
There are five pairs of road wheels per side. Track centerguides fit between each pair of road wheels. Road wheels and
torsion bars are connected to support arms. The torsion bars act as springs to keep the road wheels on the ground and from
hitting the bottom of the carrier.
ELECTRICAL SYSTEM
The electrical system provides power for the carrier. The system operates on wet cell batteries and includes charging,
regulating and monitoring equipment. The batteries provide a normal operating 24 volts with an amperage capability of 200
amps per hour.
The batteries supply the carrier with electricity when the engine is off. All electrical power is delivered through the
distribution box. Electrical power flows from the batteries through the distribution box, cables, and wiring assemblies to the
electrical equipment. The hull is a ground for the electrical system.
The generator recharges the batteries and supplies electricity while the engine is running. The generator has 200 amps per
hour capability.
There are several electrical subsystems within the hull. Each subsystem contains at least one wiring assembly. Major
electrical subsystems and assemblies are:
Interior and Exterior Lights. Exterior lights include standard headlights, infrared headlights, taillights/stoplights, and blackout
lights. Interior lights include domelights and panel lights.
Starting and Charging. A generator with a regulator keeps the batteries charged to operating voltage. A starter with a built-in
solenoid is used to crank the engine for starting.
Ventilation and Heating. All carriers have a manual open-close ventilator located at the rear of the crew compartment. The
M577A3, M981A3, and M1068A3 carriers also include an electric ventilation fan controlled by a switch on the master switch
panel (M577A3 and M1068A3) or by a switch on the fan housing (M981A3). The personnel heater is controlled by a heater
control box which provides electric power for starting and operating the heater. The control box is connected to the carrier
batteries so that the heater can be operated without turning the MASTER SWITCH ON.
Bilge Pumps. Two pumps, one in the front and one in the rear of the carrier, remove any water that may have entered the
carrier. Both pumps are controlled by a switch on the driver’s instrument panel.
SPECIAL EQUIPMENT
For information on special purpose kits, refer to Chapter 22.
WINTERIZATION EQUIPMENT
Personnel heaters are standard equipment on M577A3, M901A3, M981A3, M1068A3, and M58 carriers. Since maintenance
of heater components is the same for both standard heaters and kit heaters, they are only covered in one place in this manual.
See Chapter 22 for maintenance of heater components.
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