TROUBLESHOOTING THE HMMWV - OD1616 - LESSON 1/TASK 2
scale. The heater core fits into the heater unit and is connected to
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
The temperature control valve can be either
cable-operated or it can be operated by a vacuum-actuated diaphragm
that receives its vacuum supply from the engine.
(b) Heater Control Knobs and Valves.
The heater core on the
HMMWV has a mechanically-actuated, mechanically-controlled butterfly
valve that is opened, adjusted, and closed by the operator pulling a
control knob. This control knob is connected to one end of a cable,
the other end is connected to the butterfly valve. When the operator
pulls the knob, the cable pulls the valve actuating lever, opening
the valve. There is also a cable-operated flapper valve that allows
the operator to direct the air to either the windshield vents or to
the cab outlet.
(c) Blower Motor. The blower motor is a simple electric motor
that drives a circular fan.
This circular fan is commonly referred
to as a squirrel cage. The blower motor on the HMMWV is controlled
by a three-position switch which allows the operator to select the
fan speed. The fan speed selections are OFF-LOW-HI. The switch, in
conjunction with a multiple element resistor, provides the circuitry
to make these motor selections possible.
(13) Trailer Receptacle. The HMMWV trailer receptacle, mounted on
the rear of the vehicle body, is protected by a spring-loaded door
and is compatible with all standard military trailer wiring circuits.
(14) Slave Receptacle.
A slave receptacle, located on the front
side of the battery box, provides for inter-vehicle cable-starting.
The slave receptacle is compatible with all NATO vehicles.