TM-9-2320-280-34
TRUCK, UTILITY: M998 SERIES
TECHNICAL MANUAL; DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE
JANUARY 1996
TM-9-2320-280-34 - Page 367 of 1258
TM 9-2320-280-34
6-5.
200 AMPERE ALTERNATOR (12338796-1) TESTING AND REPAIR (Cont ’d)
c.
Static Testing
NOTE
Refer to disassembly for component removal, if necessary.
1.
Perform Stator Test.
(a)
Remove six nuts and phase leads from diodes in front housing.
(b)
Set ohmmeter to XI scale and zero ohmmeter.
(c)
Connect ohmmeter leads between each successive pair of stator phase leads "P1"-'P2", 'P2"-"P3",
and "P1"-'P3".
Ohmmeter should read less than 1 ohm.
If ohmmeter reads infinity (o), the stator is
open, replace alternator.
(d)
Set ohmmeter to X10 scale and zero ohmmeter.
(e)
Connect ohmmeter leads between each phase lead, "P1", 'P2", and 'P3" and the ground terminal
on outside of front housing.
Ohmmeter should read infinity (o).
If ohmmeter reads zero the stator
is grounded, replace alternator.
(f)
Repeat step (e) to check phase lead "P4", "P5", and "P6".
2.
Perform Field Coil Test.
(a)
Remove two nuts and field coil leads (F+, F-) from diodes in front housing.
(b)
Set ohmmeter to XI scale and zero ohmmeter.
(c)
Connect ohmmeter leads to the two field leads and measure the resistance.
Ohmmeter should
read less than 3 ohms.
If ohmmeter reads more than 3 ohms, the field coil is open, replace
alternator.
(d)
Set ohmmeter to X10K scale and zero ohmmeter.
(e)
Connect one ohmmeter lead to a field lead and the other to the ground stud on the front housing.
Ohmmeter should read infinity ( ).
If ohmmeter reads less than 100K ohms, the field coil is
grounded, replace alternator.
3.
Perform Positive Diode Test.
(a)
Set ohmmeter to X100 scale and zero ohmmeter.
(b)
Connect one ohmmeter lead to the 'B+" output stud and the other lead to each of the six diode
terminals "S".
Ohmmeter should read nearly alike for all six, either less than 600 ohms or infinity
( ).
Reverse ohmmeter leads, ohmmeter should read nearly alike for all six but opposite the first
set of readings.
If readings are not opposite, the diode rectifier assembly is BAD, replace
alternator.
4.
Perform Negative Diode Test.
(a)
Set ohmmeter to X100 scale and zero ohmmeter.
(b)
Connect one ohmmeter lead to the ground terminal and the other lead to each of the six diode
terminals "S".
Ohmmeter should read nearly alike for all six, either less than 600 ohms or infinity
( ).
Reverse ohmmeter leads, ohmmeter should read nearly alike for all six but opposite the first
set of readings.
If readings are not opposite, the diode rectifier assembly is BAD, replace
alternator.
d.
Cleaning
Clean all alternator components in accordance with paragraph 2-13.
6-42
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