TM 5-3805-258-24-1OPERATOR'S STATIONINDIVIDUAL CIRCUIT DESCRIPTIONSYSTEMS OPERATIONMAIN POWER CIRCUITThe machines have a standard disconnect switch that is in the engine com-partment by the left rear tire. This switch is to be used only when work is doneon the electrical system, or the machine is left unattended for long periods oftime. These machines have a key switch (OFF-ON-START) on the instru-ment panel. When the key switch is turned to either the ON or START posi-tions, the main power relay is activated. The main power relay sends powerto most of the electrical system through a 60 amp auto-reset circuit breaker.There is an 8 amp auto-reset circuit breaker in the circuit which sends powerto the key switch.Diode A, in the 2V9473 Diode Assembly, is used so that the main power relaywill not activate if the batteries are connected backwards. This will preventreverse polarity damage to the alternator.Diode B, in the 2V9473 Diode Assembly, is used to keep the main power relayactivated while the engine is in operation, even if the key switch is turned OFF.The main power relay will keep activated as long as the engine runs fast enoughfor the alternator to make enough voltage to keep it activated. The main powerrelay must be activated while the engine is in operation, to keep the battery loadon the alternator.CAUTIONThere can be damage to the alternator if the engine is run (with thealternator connected) without the battery load on the alternator.3-166
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