TM-9-2320-361-20

2-1/2-TON, 6x6, M44A2 SERIES TRUCKS (MULTIFUEL)

TECHNICAL MANUAL; UNIT MAINTENANCE

OCTOBER 1991
TM-9-2320-361-20

  TM-9-2320-361-20 - Page 175 of 1207

TM 9-2320-361-20
Table 2-4. Electrical Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Test 2. Test charging system output voltage.
Step 1. Open door of battery compartment. Loosen two thumbscrews and slide batteries onto
running board.
Step 2. Use multimeter to check battery voltage.
NOTE
If vehicle is equipped with a slave receptacle, check voltage at
receptacle.
Step 3. Start engine (TM 9-2320-361-10).
Step 4. Set engine speed at 1200 rpm.
Step 5. Turn vehicle headlights and accessories to ON position.
Step 6. Use multimeter to check battery voltage. Charging voltage on batteries should be
28.0 ± 0.2 Vdc.
a.
b.
c.
d.
e.
f.
If battery voltage measures 24.0 Vdc, alternator has no output. Go to test 3 and check
input voltage.
If battery voltage is between 24.0 and 26.0 Vdc, alternator output is weak. Go to test 3
and check input voltage.
If battery voltage measures 28.0 ± 0.2 Vdc and battery generator on instrument panel
shows no voltage, an electrical problem exists between generator and accessory/ignition
switch. Go to malfunction 2, test 4, step 3.
If battery voltage measures between 26.0 and 30.0 Vdc, adjust voltage regulator
(para. 4-3) in alternator until voltage across batteries is 28.0 ± 0.2 Vdc. Go to step 7 and
check regulator stability.
If regulator voltage across batteries cannot be adjusted to 28.0 ± 0.2 Vdc, replace
alternator (para. 4-3).
If battery voltage is greater than 30.0 Vdc, first try to adjust voltage regulator in
alternator down to 28.0 Vdc. If voltage regulator voltage cannot be adjusted to
28.0 Vdc, replace alternator (para. 4-3).
Step 7. Check voltage regulator stability as follows:
a.
b.
c.
d.
e.
f.
g.
Decrease engine speed to 1000 rpm with headlights in ON position. Regulated battery
voltage should remain at 28.0 ± 0.2 Vdc.
If battery voltage drops below 27.5 Vdc, replace alternator (para. 4-3).
Increase engine speed to 2000 rpm. Regulated battery voltage should remain at
28.0 ± 0.2 Vdc.
If battery voltage increases above 28.5 Vdc, replace alternator (para. 4-3).
Return engine speed to 1200 rpm.
Turn headlights OFF and ON and observe change of battery voltage.
If battery voltage changes more than ± 0.5 Vdc and does not return quickly to
28.0 ± 0.2 Vdc, replace alternator (para. 4-3).
2-90


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