TM 9-2350-247-20-1
THEORY OF OPERATION — Continued
0003 00
The vehicle compartment heater system provides heat inside the carrier. Major parts are the combination combustion
chamber/heat exchanger, blowers, a fuel pump, and an electrical control. The heater operates using diesel fuel pumped from
the fuel tank. Fuel is delivered to the combustion chamber from the fuel pump. Outside air is drawn into the combustion
chamber by one of the blowers. A blower draws air from the crew compartment into the heater exchanger. The air is warmed
by heat created by the combustion process and then returned to the crew compartment.
The electrically driven bilge pump removes water at a rate of 46 gpm (gallons per minute) and other liquids from the hull.
Water enters the pump through a screened inlet. The pumps force water out of the carrier through an outlet tube. The bilge
pump is controlled by a switch on the driver’s panel.
The fire extinguisher system consists of Carbon Dioxide (CO2) cylinders; one fixed and one portable. CO2 can put out fires
quickly and effectively. The fixed cylinder is located near the driver’s compartment and is operated manually by pulling
cables located on top of carrier next to driver’s door. The fixed cylinder releases CO2 in the power plant compartment only.
The portable fire extinguisher is located in the crew compartment and is manually discharged.
KIT INTEGRATED SYSTEMS
SPECIAL PURPOSE KITS
When special purpose kits are installed, their systems and components become integrated with the carrier’s systems and
components. The carriers may be equipped with any of the following special purpose kits.
VEHICLE COMPARTMENT (PRIMARY) KIT (M548A1)
The vehicle compartment (primary) heater kit provides heat for personnel and windshield defrosting in cold weather. The
carrier can be equipped with any one of three vehicle compartment heater kits. Each kit includes a heater, fuel system,
exhaust system, electrical system, and an air circulating system. Kit I takes in air through a duct in the power plant
compartment and has a tubular heat defroster manifold which crosses the width of the cab below the windshields and a duct
that supplies heated air to the crew compartment. Kit II takes in cab air through a duct behind the driver’s seat and has two
defroster ducts, a separate duct to heat the driver’s footwell, and a crew compartment heat distribution duct or manifold. Kit
III is identical to Kit II except that there is no regulator valve, and two fans with individual on-off switches circulate cab air to
the defroster ducts instead of air from the heater.
One of two basic heater models are furnished with the vehicle compartment heater kits. Both heaters are electrically
controlled multi-fuel heaters capable of burning any hydrocarbon fuel. Air is drawn in at the top for heating and combustion.
Heated air is forced out the bottom. Combustion gases are discharged outside the carrier. The heaters contain an electric glow
plug, flame detector switch, and an overheat switch.
All three heater kits have the same fuel, exhaust, and electrical systems. Heater fuel system consists of an electric fuel pump
and related fuel lines and fittings. Exhaust system consists of an exhaust pipe which carries exhaust gases outside the carrier.
Electrical system consists of a wiring harness and a heater control box, with the Kit III wiring harness also connecting the left
and right defrost fans with two on-off control switches.
Air circulating system consists of a two stage blower, hoses and ducts, and an outlet manifold in the cab. In Kits II and III, air
is drawn from behind the driver’s seat into the heater. In Kit I, air is drawn from the cargo area. Kits I and II have adjustable
outlet ducts in the manifold. Kit III has two defrost fans in the system.
VEHICLE COMPARTMENT (SECONDARY) HEATER KIT (M548A1)
The vehicle compartment (secondary) heater kit is used with the vehicle compartment (primary) heater during extremely cold
weather, –25
to –65
F (–31
to –54
C). The kit contains a cab cover, fabric machine gun hatch cover, lower cab insulation
and thermal door windows, and seat covers for driver and personnel seats.
0003 00-15
