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 range.

2. NO-CHARGE INDICATOR (fig. 2-76) is set up to indicate whenever the alternator is not producing current.

FUEL GAUGE

Most fuel gauges are operated electrically and are composed of two units - the 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.