Service Manual

Table Of Contents
7. Troubleshooting 10-2019
150 A062J683 (Issue 1)Copyright © 2019 Cummins Inc.
20. Measure 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.
21. Check the battery heater to make sure if it is functioning properly (if applicable).
a. Verify that the heater thermostat is functioning properly.
b. If a battery heater is recommended for ambient temperature and not
installed, install a battery heater.
22. Check that correct oil is being used for ambient conditions. If not, change oil.
a. If present, verify that oil heater is functioning properly. Repair if necessary.
b. If an oil heater is recommended and not installed, install an oil heater.
c. Verify that heater thermostat is functioning properly.
23. Measure quad voltage during cranking. If below 15 VAC during cranking,
inspect the excitation system. Field voltage should equal battery voltage (12
VDC nominal) during cranking. If not, replace the generator set control.
Code 12 - Overvoltage
Logic:
Instantaneous Fault: AC voltage S1-S2 greater than 300 VAC
Delayed Fault: AC voltage line-to-line greater than 268 VAC, but less than 300
VAC for 3 continuous seconds.
Possible Causes:
Generator set loads
Wire connections
Alternator windings
Faulty voltage regulator
Sticking governor linkage
Diagnosis & Repair:
1. Check the last fault recorded.
If this fault has not been repaired, troubleshoot that fault.
2. Measure and verify the AC voltage at the generator set circuit breaker and at
pins P1-34 and P1-35.
3. Verify the AC frequency on the display, then measure it on a digital volt
ohmmeter. Compare the two measurements to determine if the control is
measuring frequency correctly.
If the compared measurements are not consistent, replace the control
board.
4. Cycle loads to determine if a particular load causes fault.
Diagnose faulty load if necessary.