ELECTRICAL SYSTEM - continued - TM-9-2320-391-100092

TM 9-2320-391-10

M1078A1 SERIES THEORY OF OPERATION -

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Continued

ELECTRICAL SYSTEM - Continued

Alternator, Battery, and Starting Systems (Vehicle S/N 18,550 to 199,999). The

vehicle Electrical System is a combined 12/24 VDC system. Four 12-volt batteries are

connected in series-parallel with the negative terminal grounded to the vehicle chassis.

1. Positioning the master power switch to on applies power to all electrical circuits

needed to operate the vehicle.

2. The starting motor operates directly from the 24 VDC source through the starter

pushbutton.

3. A Dual-Voltage, 100 Amp belt-driven alternator maintains the charge on the batteries.

This alternator can operate without the batteries, and provides a trickle charge to the

batteries while they are disconnected. The alternator also includes two on-board

LED's one for the 12 VDC output and one for the 24 VDC output. See Table 1.

Alternator LED Status for more information. The 24 VDC source supplies electrical

power to operate the starting motor, Central Tire Inflation System (CTIS), fuel/water

separator, air dryer, ether injection system, instrument panel assembly gages, and

windshield wipers/washer. The 12 VDC source supplies electrical power to the vehicle

lights and instrument panel assembly lights.

Table 1. Alternator LED Status.

LED COLOR

SYSTEM STATUS

OFF

Regulator is not energized

FLASHING

Green

The respective system voltage (12 or 24

VDC) is normal.

Amber

The respective system voltage (12 or 24

VDC) is low.

Red

The respective system voltage (12 or 24

VDC) is high.

STEADY

Red

The alternator is shut down and is not

producing power for either voltage (12 or 24

VDC).

4. The system monitors battery voltage and alternator performance. If the batteries fail,

the Load and Battery Control Device (LBCD) provides a ground to the battery

disconnect relay, disconnecting the batteries from the electrical system and

illuminating the BATTERY DISCONN indicator on the lighted indicator display. The

vehicle continues to run off the alternator, and a trickle charge is provided to the

batteries. Once the batteries reach an acceptable voltage level, the LBCD removes the

ground from the battery disconnect relay, and the batteries are reconnected to the

electrical system. If the alternator fails, the LBCD illuminates the CHARGING SYSTEM

indicator on the lighted indicator display.

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