Figure 2-73.Ammeter schematic.
Figure 2-74.Voltmeter schematic.
system and is easier to interpret by the operator. During
vehicle operation, the voltage indicated on the
voltmeter is considered to be normal in a range of 13.2
to 14.5 volts for a 12-volt electrical system. As long as
the system voltage remains in this range, the operator
can assume that no problem exists. This contrasts with
an ammeter, which gives the operator no indication of
problems, such as an improperly calibrated voltage
regulator, which could allow the battery to be drained
by regulating system voltage to a level below normal.
The INDICATOR LAMP has gained popularity
as an electrical system condition gauge over the years.
Although it does not provide as detailed analysis of the
electrical system condition as a gauge, it is considered
more useful to the average vehicle operator. This is
because it is highly visible when a malfunction occurs,
whereas a gauge usually is ignored because the average
vehicle operator does not know how to interpret its
readings. The indicator lamp can be used in two
different ways to indicate an electrical malfunction,
which are as follows:
1. LOW VOLTAGE WARNING LAMP (fig.
2-75) is set up to warn the operator
whenever the electrical system voltage has
dropped below the normal operational
2. NO-CHARGE INDICATOR (fig. 2-76) is
set up to indicate whenever the alternator is
not producing current.
Most fuel gauges are operated electrically and are
composed of two unitsthe gauge, mounted on the
instrument panel; and the sending unit, mounted in the
fuel tank. The ignition switch is included in the fuel
gauge circuit, so the gauge operates only when the
ignition switch is in the ON position. Operation of the
electrical gauge depends on either coil action or
Figure 2-75.Low voltage warning lamp schematic.