Figure 6-28.--Testing diodes with an ohmmeter.
the ohmmeter leads to the diode, and again note the
connected between any of the stator leads and the stator
reading. If both readings are very low or very high, the
frame indicates a grounded winding. It is not practical
diode is defective. A good diode will give one low and
to test the stator windings for shorts because of the very
one very high reading. An alternate method of testing
low resistance of the windings. However, if all other
each diode is to use a test lamp with a battery having a
test results are within specifications and the generator
voltage no greater than that of the system being tested.
will not produce rated output, shorted stator windings
Connect one of the test leads to the diode lead, and
the other test lead to the diode case, as shown in figure
Testing the Diodes
6-29. Then, reverse the lead connections. If the lamp
lights in both checks, the diode is defective. If the lamp
With the stator windings disconnected, each diode
fails to light in either direction, the diode is defective.
may be tested with an ohmmeter by connecting one test
When you are checking a good diode, the lamp will
lead to the diode lead and the other to the diode case, as
light in only one direction.
shown in figure 6-28. Note the reading. Then, reverse
Figure 6-29.--Testing diodes with a test lamp.