Service Manual

7. Troubleshooting 10-2019
154 A062J683 (Issue 1)Copyright © 2019 Cummins Inc.
10. Check the generator set fuel lines for damage.
• Replace the fuel line if necessary.
11. Check the governor actuator, actuator linkage, and throttle shaft for free smooth
motion without slop. Verify that the actuator is opening the throttle while
cranking.
12. Measure the field, quadrature, and main winding resistance.
• Clean the slip rings, replace the brushes, repair the harness, and replace
the rotor and stator assembly if necessary.
13. Check brush alignment:
a. Inspect brush wear on the slip rings and verify brush misalignment is
toward the windings.
b. If the misalignment is toward the bearing, the cause is not a tolerance
issue but is more likely the result of the end bell not being seated properly
during assembly.
• Inspect for cause and repair if necessary.
Code 15 - Underfrequency
Logic: Frequency less than 54 Hz (for the 60 Hz model) for 8 continuous seconds.
Possible Causes:
• Generator set loads
• Engine governor function
• Fuel supply
• Air fuel mixture
• Exhaust system
• Demand regulator
• Throttle plate
• Alternator windings
• Ignition
• Wire connections
Diagnosis & Repair:
1. Check the last fault recorded.
• If this fault has not been repaired, troubleshoot that fault.
2. Verify that DC voltage is fully opening the shutoff valve. If it failed to open,
replace the shutoff valve.
3. Measure the AC current while running the generator set with loads.
• Identify faulty or short cycling loads.
4. Measure the generator set load capability with load bank; derate for altitude and
temperature if necessary.