TROUBLESHOOTING THE HMMWV - OD1616 - LESSON 1/TASK 2
start the vehicle.
Circuit 6A connects the batteries and the
starter; however, it is also connected to the protective control box
(PCB), which will be discussed later in this text.
(2) Alternator.
Most military vehicles are equipped with an
alternating current (ac) charging system. The reason for changing to
the ac system is that an alternator is capable of producing a higher
voltage at idle speed.
Many of the military vehicles are equipped
with radios, a firing device, and other high-current-drawing
equipment.
When this equipment is in operation and the vehicle's
engine is operating at a low rpm, a dc generator will not produce the
required current and voltage to keep the batteries charged plus
supply the current required to operate the accessories properly.
Alternators convert mechanical energy to electrical energy which is
used to power the vehicle.
(a) Basic Alternator Construction.
The alternator is composed
of the same basic parts as a direct current (dc) generator. There is
a field that is called a rotor and a generating part known as the
stator. The purpose of the alternator is to produce more power and
operate over a wider speed range than that of a generator. Because
of this, the construction of the functional parts is different. The
stator is the section in which the current is induced. It is made of
a slotted, laminated ring with the conductors placed in the slots.
The current generated in the windings is transferred to the rest of
the system through three stationary terminals.
(b) One of three different amperage rated alternators can be
found on the HMMWV. One is the 60 amp alternator which is similar to
the alternator used on the M151. It is mounted on the left side of
the engine and is driven by dual drive belts from the crankshaft
pulley. A slotted bracket allows for belt tension adjustments. The
other two alternators are the 100 amp alternator which is found
primarily on the shelter carriers (M998 and M1037), and the 200 amp
alternator which is used mainly on the ambulance (M996 and M997).
(3) Starter.
Any internal combustion engine must be cranked
manually to start it running on its own.
Early automotive vehicles
were started by the driver through the use of a handcrank. A system
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