Guardian 4389 Repair Manual page 41

AC GENERATORS
TEST 7: TESTING THE STATOR WITH A VOM
DISCUSSION:
A Volt-OHM-Milliammmeter (VOM) can be used to
test the stator windings for the following faults:
• An open circuit condition
• A "short-to-ground" condition
• A short circuit between windings
Note: The resistance of stator windings is very
low. Some meters will not read such a low resis-
tance, and will simply indicate CONTINUITY.
Recommended is a high quality, digital type meter
capable of reading very low resistances.
PROCEDURE:
1. Disconnect stator leads 11 and 44 from the main circuit
breaker.
2. Disconnect stator leads 22 and 33 from the neutral con-
nection separate the leads.
3. Disconnect Connector C2 from the side of the control
panel (C2 is the closest to the back panel, see Figure 9,
Section 6).
4. Make sure all of the disconnected leads are isolated
from each other and are not touching the frame during
the test.
5. Set a VOM to its "R x 1" scale and zero the meter.
6. Refer to Figure 5 for pin locations of Connector C2. Use
a large paper clip or similar metallic object to access
pins in connector C2 (Female Side).
Note: Pins 9, 10, 11 & 12 are not used for this test.
1 12
2 11
3 10
4 9
5 8
6 7
FEMALE SIDE
Figure 5. C2 Connector Pin Locations
7. Connect one test lead to stator lead Wire 11. Connect
the other test lead to stator lead Wire 22 (power wind-
ing). Note the resistance reading and compare to the
specifications in the front of this manual.
8. Connect one test lead to stator lead Wire 33. Connect
the other test lead to stator lead Wire 44 (power wind-
PART 2
12 1
11 2
3
10
4
9
5
8
6
7
MALE SIDE
ing). Note the resistance reading and compare to the
specifications in the front of this manual.
9. Connect one test lead to Pin 1. Connect the other test
lead to Pin 2 (battery charge winding). Note the resis-
tance reading, compare to specifications in the front of
this manual.
10.Connect one test lead to Pin 3. Connect the other test
lead to Pin 4 (engine run winding). Note the resistance
reading, compare to specification in the front of this
manual.
11.Connect one test lead to Pin 5. Connect the other test
lead to Pin 6 (power winding-sense leads). Note the
resistance reading, compare to specification in the front
of this manual.
12.Connect on test lead to Pin 7. Connect the other test
lead to Pin 8 (excitation winding). Note the resistance
reading, compare to specifications in the front of this
manual.
TEST WINDINGS FOR A SHORT TO GROUND:
13. Make sure all leads are isolated from each other and
are not touching the frame.
14. Set a VOM to its "R x 10,000" or "R x 1K" scale and zero
the meter
15. Connect one test lead to a clean frame ground.
Connect the other test lead to stator lead Wire 11.
a. The meter should read INFINITY.
b. Any reading other than INFINITY indicates a
"short-to-ground" condition.
16. Repeat Step 15 using stator lead Wire 33.
17. Repeat Step 15 using Pin 1.
18. Repeat Step 15 using Pin 3
19. Repeat Step 15 using Pin 5
20. Repeat Step 15 using Pin 7
TEST FOR A SHORT CIRCUIT BETWEEN WINDINGS:
21. Set a VOM to its "R x 10,000" or "R x 1K" scale and zero
the meter.
22. Connect one test lead to stator lead Wire 11. Connect
the other test lead to stator lead Wire 33.
a. The meter should read INFINITY.
b. Any reading other than INFINITY indicates a
short circuit between windings.
23.Repeat Step 22 using stator lead Wire 11; Pin 1
24.Repeat Step 22 using stator lead Wire 11; Pin 3
25.Repeat Step 22 using stator lead Wire 11; Pin 7
26.Repeat Step 22 using stator lead Wire 33; Pin 1
SECTION 2.4
DIAGNOSTIC TESTS
Page 39