TM 9-2320-272-10
1-19.
ELECTRICAL SYSTEMS OPERATION (Contd)
A
VOLTMETER - Indicates system voltage and is connected to the batteries through circuit 27 and to chassis
ground through instrument panel.
B
ENGINE COOLANT TEMPERATURE INDICATOR - Indicates engine coolant temperature and receives battery
power through circuit 27. Circuit 33 completes the circuit to ground through a coolant temperature sensor that
reacts to changes in engine coolant temperature by increasing or decreasing the resistance in the ground circuit.
C
ENGINE OIL PRESSURE INDICATOR - Indicates engine oil pressure and receives battery power through circuit
27. Circuit 36 completes the circuit to ground through the oil pressure transmitter located on the engine block.
D
FUEL INDICATOR - Indicates fuel level. Receives battery power through circuit 27. Circuit 28 or 29, depending
upon which position the fuel selector switch is in, completes the circuit to ground through the fuel level sensor.
E
TRANSMISSION OIL TEMPERATURE INDICATOR - Indicates transmission oil temperature and receives battery
power through circuit 27. Circuit 324 completes the circuit to ground through a temperature sensor located in the
transmission.
F
FRONT-WHEEL DRIVE ENGAGEMENT LIGHT - Informs the operator that the front-wheel drive is engaged. The
system consists of a normally open pressure switch, which is powered through circuit 27A and an indicator lamp
powered through circuit 27A.
G
HORN SYSTEM - The horn system consists of an air-operated horn that is controlled by an electric solenoid. The
solenoid is powered through circuit 26 and controlled by the horn switch through circuit 25.
H
SPRING BRAKE WARNING SYSTEM - Warns the operator that the spring brakes are applied. The system
consists of normally open pressure switch powered through circuit 37 and an indicator lamp which is powered
through circuit 37.
I
FAILSAFE WARNING - SYSTEM Intended to give the operator an audible as well as visual signal of a malfunction
in one of the primary systems. Power for the system is supplied from the ignition switch through circuit 564. The
failsafe module causes an indicator lamp to illuminate and an alarm to sound when the air pressure falls below 60
psi (414 kPa) or when the parking brake is set.
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