Diesel generator sets are widely used as reliable backup or primary power sources across industries. However, during operation, issues such as no power generation or abnormal voltage output may occur. Understanding the root causes and applying the correct solutions is essential to ensure stable and continuous power supply.
Below is a comprehensive troubleshooting guide for common problems and their solutions.
Blown Fuse
Cause: Fuse damage due to overload or short circuit.
Solution:
After confirming that the circuit is normal, replace the fuse with a new one and reconnect the system.
Faulty Voltmeter
Cause: The panel meter is damaged or not displaying correctly.
Solution:
Use a multimeter (voltage mode) to directly measure the generator terminal voltage to verify actual output.
Inaccurate Meter Reading
Cause: Long-term use without calibration leads to deviation.
Solution:
Regularly calibrate the meter. Replace it if inaccuracies persist.
Poor AVR (Automatic Voltage Regulator) Connection
Cause: Loose or poor contact at AVR terminals (50Hz/60Hz selection pins, terminals 6 and 7).
Solution:
Inspect and ensure all AVR connections are secure and properly fitted.
Surge Suppressor Short Circuit
Cause: Internal short circuit or component contact (e.g., diode stack touching).
Solution:
Check the surge suppressor assembly to ensure no physical contact or shorting exists.
Rotating Diode Failure
Cause: Damaged diodes in the rotating rectifier assembly.
Solution:
Disconnect the wires connecting the rotating rectifier to the main rotor field. Test the diodes using a multimeter or test lamp. Replace faulty diodes if necessary.
Loss of Residual Magnetism
Cause: Long-term shutdown or improper operation may cause loss of residual magnetism.
Solution:
Re-magnetize the exciter stator coil using a 12V battery:
- Positive terminal → F (red wire)
- Negative terminal → F- (black wire)
Apply for 15–20 seconds.
⚠️ Ensure the generator is completely stopped during this process.
Incorrect Wiring
Cause: Improper electrical connections during installation or maintenance.
Solution:
Carefully inspect all wiring and reconnect according to the wiring diagram.
Open Circuit in Exciter Field Coil
Cause: Broken or disconnected coil wiring.
Solution:
Reconnect the broken section, solder securely, and insulate properly.
Loose or Poor Connections
Cause: Oxidation, vibration, or improper installation.
Solution:
Clean all terminals and reconnect firmly.
Generator Armature Coil Open Circuit
Cause: Internal disconnection in the armature winding.
Solution:
Locate the fault point, re-solder, and insulate.
Generator Armature Coil Short Circuit
Cause: Insulation failure causing internal shorting.
Solution:
Replace the damaged coil immediately to prevent overheating and further damage.
Exciter Armature Coil Fault (Open or Short Circuit)
Cause: Damage in exciter armature windings.
Solution:
Identify the fault and replace the coil.
Abnormal Speed
Cause: Engine speed not within rated range, affecting voltage and frequency.
Solution:
Use a tachometer or frequency meter to check speed and adjust accordingly.
AVR Protection Shutdown
Cause: AVR protection function activated due to abnormal conditions.
Solution:
Reset and adjust the AVR according to the manufacturer's manual.
AVR Failure
Cause: Internal failure of the automatic voltage regulator.
Solution:
Replace the AVR with a new unit.
When a diesel generator fails to produce power or outputs unstable voltage, the issue is often related to electrical components, wiring, excitation systems, or control devices. Systematic inspection and timely maintenance can effectively prevent downtime and extend equipment lifespan.
At Dianbida Power Equipment (Jiangsu) Co., Ltd., we provide high-performance diesel generator sets along with professional technical support and after-sales service to ensure reliable operation in all conditions.
