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Insulation Resistance Test
This test measures the quality of the insulation
materials that keep the electrical windings and
the generator's steel core seperated.
Dust, dirt, and moisture can cause the insulation
to erode over time. Most winding failures are due
to a failure in the insulation system.
Winding insulation can be checked on the main
stator and rotor and on the exciter stator and
rotor.
1. Set SYSTEM switch to OFF.
2. Remove the 15 Amp system control panel
fuse and disconnect the negative (-)
battery cable.
3. Remove all regulators, diodes, surge
protectors, capacitors and relays from the
winding circuit before testing.
4. Using a mega-ohm meter, check for a
minimum insulation resistance of 2 mega-
ohms.
• If insulation resistance is acceptable,
proceed to Diode Test.
• If insulation resistance is not
acceptable, repair or replace as
necessary.
Diode Test
NOTE: To access diodes, the engine must be
rolled over. Contact engine manufacturer for
instructions on how to roll over engine.
1. Remove the 2 main rotor leads from the
rectifier assembly.
2. Remove the 3 exciter rotor leads fro the
rectifier assembly.
• The diodes and the diode test leads will
remain mounted to the posts during the
testing process.
3. Using meter set to measure Ohms (Ω),
place one test lead on the diode lead
terminal post.
4. At the same time, touch the other test lead
to the diode mounting nut (Figure 31).
Figure 31
5. Reverse the test lead probes and repeat
Steps 3 and 4 (Figure 32).
Figure 32
6. Using Steps 3-5, test the six diodes in the
forward and the reverse directions.
• If the diode is GOOD, greater
resistance will be measured in one
direction more than the other.
• If the diode is SHORTED, the meter will
read "0" or, the resistance will be very
low in both directions. Replace the
rectifier assembly if one or more diodes
are SHORTED.
• If the diode is OPEN, the meter will
have an infinity reading in both
directions. Replace the rectifier
assembly if one or more diodes are
OPEN.
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