Section 1 AC Diagnostic Tests
14 Diagnostic Repair Manual
Test 8 – Test Brushless Stator
Windings
General Theory
The brushless stator has three internal windings, two
main power windings and a DPE winding. This test will
ensure there are no shorts between the power windings
or shorts to ground.
A DMM meter 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 resistance, and will
simply indicate CONTINUITY. Recommended is a high
quality, digital type meter capable of reading very low
resistances.
NOTE: See Figure 1-4 in Section 1, Configuration “A”.
Some wire numbers will not be marked on the stator.
Procedure
1. Disconnect Wires 11, 22, 33, 44 from the
receptacle panel so the stator is isolated.
2. Verify all the disconnected leads are isolated from
each other, and are not touching the frame during
the test.
3. Set DMM to measure resistance.
4. Connect one test lead to Stator Lead 11. Connect
the other test lead to Stator Lead 22. Stator
resistance should be between 0.12-0.14 Ohms.
5. Connect one test lead to Stator Lead 33. Connect
the other test lead to Stator Lead 44. Stator
resistance should be between 0.12-0.14 Ohms.
Test windings for a short-to-ground:
1. Verify all leads are isolated from each other and
are not touching the frame.
2. 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.
3. Repeat Step 2 using Stator Lead 44.
Test for a short circuit between windings:
1. Connect one test lead to Stator Lead 11. Connect
the other test lead to Stator Lead 33.
a. The meter should read INFINITY.
b. Any reading other that INFINITY in
dicates a
sh
ort between windings.
Test 9 – Test Brushed Stator Windings
General Theory
Most brushed stators have three main windings that are
needed to produce voltage. The alternator has two main
power windings which supply power to the load and a
DPE winding to provide excitation voltage to the rotor.
These windings must remain isolated from ground or the
chassis of the alternator.
Procedure
1. Isolate all stator wires from the control panel and
voltage regulator
.
2. Set DMM to measure resistance.
3. See Figure 2-3 for proper test points to check the
stator. Every connection needs to be checked
coming out of the stator for a short to ground
.
Results
1. If any wire has a direct short-to-ground, or to the
chassis of the alternator, replace alternator
assembly
.
2. If all wires test good for a short-to-ground, refer to
flow chart.
Test 10 – Check Load Voltage &
Frequency
Procedure
Perform this test the same as Test 1 but apply a load to
the generator equal to its rated capacity. Check voltage
and frequency with load applied.
Frequency should not drop below about 59 Hertz.
Voltage should not drop below about 220 VAC nor rise
above 265 VAC.
Results
1. If voltage and/or frequency drop excessively when
load is applied, refer to flow chart.
2. If load voltage and frequency are within limits, end
tests.
Test 11 – Check Load Watts &
Amperage
Procedure
Add up the wattages or amperages of all loads powered
by the generator at one time. If desired, a clamp-on
ammeter may be used to measure current flow.
See the Wattage Reference Guide to determine
generator limits.
NOTE: All figures are approximate. See data label on
appliance for wattage requirements.
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