Learning Objective: Identify instrument, gauges, and accessories, their functions, and maintenance procedures.

The instrument panel is placed so that the instruments and gauges can easily be read by the operator. They inform the operator of the vehicle speed, engine temperature, oil pressure, rate of charge or discharge of the battery, amount of fuel in the fuel tank, and distance traveled. Vehicle accessories, such as windshield wipers and horns, provide the operator with much needed safety devices.

BATTERY CONDITION GAUGE
The battery condition gauge is one of the most important gauges on the vehicle. If the gauge is interpreted properly, it can be used to troubleshoot or prevent breakdowns. The following are the three basic configurations of battery condition gauges- ammeter, voltmeter, and indicator lamp.

The AMMETER is used to indicate the amount of current flowing to and from the battery. It does NOT give an indication of total charging output because of other units in the electrical system. If the ammeter shows a 10-ampere discharge, it indicates that a 100 ampere-hour battery would be discharged in 10 hours, as long as the discharge rate remained the same. Current flowing from the battery to the starting motor is never sent through the ammeter, because the great quantities of amperes used (200 to 600 amperes) cannot be measured due to its limited capacity. In a typical ammeter (fig. 2-73), all the current flowing to and from the battery, except for starting, actually is sent through a coil to produce a magnetic field that deflects the ammeter needle in proportion to the amount of current. The coil is matched to the maximum current output of the charging unit, and this varies with different applications.

The VOLTMETER (fig. 2-74) provides a more accurate indication of the condition of the electrical

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.