4-12
CHARGING
4-12
TESTING (Continued)
Diode Test
Remove the rectifier assembly from the alter-
nator. Set the ohmmeter “Multiply By” knob at 1
and calibrate the meter as directed.
CAUTION: Digital meters cannot be used to
perform these diode tests.
1.
To test one set of diodes, contact one probe to
the terminal bolt and contact each of the three
stator lead terminals with the other probe. Re-
verse the probes and repeat the test. All di-
odes should show a low reading of about 6
ohms in one direction and an infinite reading
(no needle movement) with the probes re-
versed. The low reading may vary with the
type of tester used. This reading may be
checked against a good rectifier if it is
available.
OHMMETER
PROBES
.
OHMME(ER & /-
CONTACT EACH
TERMINAL
J31534A
2. Repeat the preceding tests for the other set of
diodes except that the other terminal screw is
used.
3. If the meter readings are not as specified,
replace the rectifier assembly.
Stator Coil Grounded Test
These tests are made to determine if the stator
coil is operating properly. Remove the stator from
the alternator and disconnect from the rectifier
assembly (refer to Disassembly procedure in this
section). Set the ohmmeter “Multiply By” knob at
1000.
1. Connect the ohmmeter probes to one of the
stator leads and to the stator laminated core.
Be sure that the probe makes a good elec-
trical connection with the stator core. The
meter should show an infinite reading (no
meter movement).
2. If the meter does not indicate an infinite read-
ing (needle moves), the stator winding is
shorted to: the core and must be replaced.
3. Repeat this test for each of the stator leads.
Do not touch the metal probes or stator leads
with the hands. Such contact will result in an
incorrect reading.
Stator Coil Open Test
This test determines if there is an open stator
circuit. Disconnect the stator from the rectifier as-
sembly. Set the ohmmeter “Multiply By” knob at
1.
1. Connect one ohmmeter probe to a stator
phase lead and touch the other probe to an-
other stator lead. Check the meter reading.
OHMMETER
STATOR
2. Repeat this test with the other two stator lead
combinations. If no meter movement occurs
(infinite resistance) on a lead paired with ei-
ther of the other two leads, that phase is open
and the stator should be replaced.
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