TP-5867 11/02 41Section 6 Component Testing and Adjustment
Hazardous voltage.
Can cause severe injury or death.
Operate the generator set only when
all guards and electrical enclosures
areinplace.
Moving rotor.
WARNING
High voltage test. Hazardous voltage can cause severe
injury or death. Follow the instructions of the test equipment
manufacturer when performing high-voltage tests on the rotor
or stator. An improper test procedure can damage equipment
or lead to generator set failure.
Short circuits. Hazardous voltage/current can cause
severe injury or death. Short circuits can cause bodily injury
and/or equipment damage. Do not contact electrical
connections with tools or jewelry while making adjustments or
repairs. Remove all jewelry before servicing the equipment.
Stator Continuity and Resistance Tests
1. Place the generator set master switch in the OFF
position.
2. Disconnect power to the battery charger, if
equipped.
3. Disconnect the generator set engine starting
battery, negative (--) lead first.
4. Disconnect all stator leads before performing all
stator tests.
5. To check for stator continuity, set the ohmmeter on
R x 1 scale. First set the ohmmeter zero by holding
the red and black meter leads together and setting
the ohmmeter reading to zero. Then check the
stator continuity by connecting the meter leads to
the stator leads as shown in Figure 6-10.
Note: Leads 1, 2, 3, and 4 are the generator output
leads. Leads 33, 44, and 55 are the voltage
regulator sensing and supply leads. Refer
to the schematic in Figure 6-11 when
performing the following steps.
6. Contact the ohmmeter leads and readjust the
ohmmeter to read zero ohms.
7. Check the cold resistance of the stator windings by
connecting the meter leads to stator leads 1-2, 3-4,
33-44, and 55-33. See Section 1.3, Alternator, for
stator winding resistances. Most ohmmeters do
not provide accurate readings below 1 ohm. Low
resistance readings (continuity) and no evidence of
shorted windings (heat discoloration) indicate a
stator in good condition.
R14807-14
Figure 6-10 Testing Stator Windings
3
4
55
2
1
44
33
5632714
Figure 6-11 Alternator Stator Leads
8. If the resistance test proves inconclusive, use a
megohmmeter to test the stator as described in the
next step.
Note: Because ohmmeter accuracy varies,
resistance readings are approximate
readings. Take readings of the rotor and
stator at room temperature.
9. Use a megohmmeter to determine whether the
stator is shorted to ground.
a. Apply 500 volts DC to any stator lead and the
stator frame. Perform the megohmmeter test
following the instructions of the megohmmeter
manufacturer.
b. Repeat the test on the other stator leads until
each coil is tested.
Note: A reading of approximately 500 kOhms
(1/2 megohm) and higher indicates a
good stator.
c. Repair or replace the stator if any reading is
less than approximately 500 kOhms. A reading
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