Figure 14-5. Testing Stator for Ground.
(2) Press the other test probe firmly to each of the
three phase (stator) lead terminals, one at a time. If you
get a low resistance reading, the stator lead is grounded.
(3) Press one test probe to one phase terminal lead.
Touch the other probe to each of the other two stator leads.
The meter should indicate low resistance when the probe
contacts each of the terminals. If it does not, the stator
Figure 14-3. Rectifier End Shield and Stator Assembly.
winding is open.
(4) Install a new stator if the old one is grounded or
c. Testing the Rotor for Shorts, Grounds, or Opens. Use
an ohmmeter to check the rotor assembly for grounded,
Figure 14-4. Testing Rectifiers with Ohmmeter.
(4) Reverse the probes, moving the probe on the
rectifier heat sink to the rectifier strap and vice versa. If
you have high resistance in one direction and low resistance
in the other, the rectifier is okay. If you have low resistance
in both directions, the rectifier is shorted. If you have high
resistance in both directions, the rectifier is open.
(5) Repeat the above procedure for all rectifiers in
both assemblies. Replace any rectifier plate that has an
open or shorted rectifier (paragraph 144).
(6) All three rectifiers
on a plate should have low
resistance readings in the same direction. If one reads low
Figure 14-6. Rotor Test.
in the opposite direction, it is the wrong polarity rectifier.
Replace the rectifier plate.
(1) Test for ground. To check for a grounded field
coil, first zero the ohmmeter. Then connect the test leads
b. Testing the Stator.
from each slip ring to the rotor shaft. The ohmmeter should
(1) Press one ohmmeter test probe firmly onto any
read infinite at each slip ring. If the reading is less than
infinite, the rotor is grounded.
has been removed so that the pin is bare.