electrical system, is provided with a fuse that has anampere rating for the maximum current required tooperate the unit.The fuse element is made from a metal that has alow-melting point and is the weakest point in theelectrical circuit. In case of a short circuit or othertrouble, the fuse burns out first and this opens the circuitjust as a switch would do. Visual examination of aburned-out fuse usually provides a quick indication ofthe problem. A discolored sight glass indicates thecircuit has a short either in the wiring or one of itscomponents. If the glass is clear, the problem may bean overload in the circuit.When replacing a fuse, you should ensure that it hasa rating equal to the one burned out. Also, ensure thatthe malfunction that caused the failure has beendetermined and repaired.GAUGESJust because everything checks out okay during theprestart operation does not mean it will stay that waythroughout the workday. You must continually monitorcertain conditions, such as water temperature, oilpressure, and so forth, to ensure the equipment isrunning correctly. You monitor them by watching theindicator (warning lights or gauges) on your equipment.On equipment, you may see an analog type of gauge (fig.4-7) or color-coded indicators, as shown in figure 4-8.Figure 4-7.—Analog gauges.Figure 4-8.-Color-coded gauges.Water Temperature GaugeWhen operating a piece of equipment, you mustmonitor the water or coolant temperature gauge. If yourmachine has an analog type of gauge (fig. 4-7), you mustknow the correct operating temperature. Refer to theoperator’s manual to determine the operatingtemperature. Anytime the temperature reading on thegauge starts to rise, stop and determine the reason. Donot wait until the gauge is in the red zone to investigate.WARNINGUse extreme caution when removing a hotradiator cap. Steam coming from the radiatorwill cause severe burns.4 - 6
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