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TM 9-8000
a magnetic effect that deflects the ammeter needle in
17-1.  Purpose (Fig. 17-1). The  instrument panel
proportion to the amount of current. This coil is matched
usually is placed so that the Instruments may be read
to the maximum current output of the generator and this
easily by the driver. They inform the driver of the
varies with different applications. Some model wheeled
approximate speed, engine temperature, oil pressure,
vehicles have replaced the ammeter with a battery
rate of charge or discharge of the battery, amount of fuel
generator indicator that does not give a calibrated
in the fuel tank, distance traveled, and the time. Certain
reading, but shows ranges by colors or bands. `
controls frequently are mounted on the Instrument board,
such as the throttle, choke, starter, heater, and
b. Voltmeter (Fig. 17-3). Voltmeters are gaining
windshield wiper.
popularity as an Instrument panel battery condition
Indicator. This is because the electrical system voltage is
17-2.  Battery  Condition  Gages.  One  of the
a more accurate indication of the condition of the
Instruments that almost always Is included on an
electrical system than the amperage and is easier to
Instrument panel is a battery condition gage. It is a very
interpret by the operator. During vehicle operation, the
Important indicator because, if interpreted properly, it can
voltage indicated on the voltmeter is considered to be
be used to troubleshoot or prevent breakdowns. The
normal in a range of 13.2 to 14.5 volts for a 12-volt
following are the three basic configurations of battery
electrical system. As long as the system voltage remains
condition gages.
in this range, the operator can assume that no problem
exists. This contrasts with an ammeter, which gives the
a. Ammeter (Fig. 17-2). The ammeter is used to
operator no Indication of problems such as an improperly
indicate the amount of current flowing to and from the
calibrated voltage regulator, which could allow the battery
battery. It does not give an indication of total generator
to be drained by regulating system voltage to a level that
output because other units in the electrical system,
is below normal.
besides the battery, are sup- plied by the generator. If it
shows a 10-ampere discharge, it indicates that a 100
c. Indicator Lamp. The indicator lamp has gained
ampere-hour battery would be discharged in 10 hours;
increasing popularity as an electrical system condition
that is, 10 amperes flowing for 10 hours. Current flowing
gage over the years. Although it does not provide as
from the storage battery to the starting motor is never
detailed an analysis of electrical system condition as a
sent through the ammeter, because the great quantities
gage, it usually is considered more useful to the average
used (200 to 600 amperes) cannot be measured on an
vehicle operator. This Is because it is highly visible when
instrument of such limited capacity. In the typical
a malfunction occurs, whereas a gage usually Is
ammeter, all the current flowing to and from the battery,
except for starting, actually is sent through a coil to
Figure 17-1. Typical Instrument Panel


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