TM-9-2350-311-20-1

HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5

TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR HULL, POWERPLANT, DRIVE CONTROLS, TRACKS, SUSPENSION, AND ASSOCIATED COMPONENTS

AUGUST 1994

TM-9-2350-311-20-1 - Page 264 of 1275

TM 9-2350-311-20-1

3-3

TROUBLESHOOTING

CHART — CONTINUED

m. ALTERNATOR CIRCUIT (M109A2/M109A3)—

ALTERNATOR FAILS TO CHARGE BATTERIES; GAGE

CONTINUED

INDICATION: NOT CHARGING, UNSTEADY OR

INACCURATE READING — CONTINUED

CONTINUED FROM STEP K

NOTE

• Batteries can be totally discharged within 4 to 6

hours if air cleaner blower motor system is

malfunctioning or if blower motors operate full

time. Troubleshooting step L provides a basic test

of blower motor circuit by testing blower motor

relay output voltage to voltage regulator (lead

27B).

• If blower motor relay output is 24 Vdc or greater

(battery power) with voltage regulator

disconnected from circuit, voltage regulator is

malfunctioning/inoperative and will not charge

battery.

• If voltage is less than 24 Vdc (battery power),

blower motor circuit is malfunctioning and

discharging battery.

I

L

1. Reconnect rectifier to voltage regulator

wiring harness to voltage regulator.

2. Disconnect battery ground leads.

3. Disconnect engine disconnect bracket-to-

bulkhead wiring harness from voltage

regulator.

4. Place jumper wires from socket A (lead 2)

to socket B (lead 400-459B), from pin C

(lead 3) to battery negative terminal, and

from pin F (lead 27B) to positive terminal

of same battery to apply 12 Vdc to

alternator field.

5. Reconnect battery ground leads.

6. Turn MASTER switch ON and run vehicle

engine at 1000 rpm (oil pressure at 12 psi [83

kPa]).

7. Place red lead of multimeters in socket F

(lead 27B) and black lead to ground.

8. Check for voltage.

Is voltage above 27.5 Vdc?

I

CONTINUED ON NEXT PAGE

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