INTRODUCTION TO THE HMMWV - OD1615 - LESSON 4/TASK 1
the windshield header. Dual ten inch blades are actuated by the linkage and
pivot from the top of the windshield frame. The blades operate in unison
and return to a "park" position at the right side of the "wipe pattern" when
the wiper switch is turned off. Windshield washing is accomplished through
two jets on the cowl below the windshield.
The fluid is contained in a
solution or water; NEVER use engine anti-freeze.
l. Heater, Defroster, and Ventilation Mechanisms.
defroster, and ventilation mechanisms are usually contained in a single unit
to make up a complete system.
The unit, which is called a heater unit,
consists of a chambered box containing a heater core and control doors which
allow the operator to select the desired mode of operation. The outside of
the box contains openings for outside air intake, so that fresh air can be
recirculated, and an interior air intake, so that inside air can be
recirculated. The box also has defroster outlets, so that forced air can be
provided to clear the windshield; heater outlets, so that heated air can be
provided, usually at floor level; and ventilation outlets, so that air can
be forced into the passenger compartment at instrument panel level.
electric blower motor is also combined with this unit to provide air
(1) Heater Core. The main component of the HMMWV's heater system is
the heater core. The heater core is the component that transfers heat from
the engine coolant to the passenger compartment.
Its construction is
similar to that of a radiator, except that it is on a much smaller scale.
The heater core fits into the heater unit and is connected to the engine's
The connection to the
engine's coolant passages is made at strategic points that will cause the
engine's water pump to force a constant supply of engine-heated coolant
through the heater core. The heater core feed line is fitted with a control
valve that can be controlled by the operator. The purpose of the valve is
to open, restrict, or shut off the coolant flow through the heater core to
control the heater temperature. The temperature control valve can be either
cable operated, or it can be operated by a