Kohler-SDMO Voltage Instability / Poor Regulation

Generator output voltage is unstable or fluctuating under steady load

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Defective AVR, Loose voltage sensing connections, Harmonic distortion from nonlinear loads, Worn engine governor causing speed hunting

How to Fix / Troubleshooting

Safety first: Reduce the load and open the generator breaker if voltage swings are severe. Only qualified personnel should work inside live electrical panels.

  • Check connections: Inspect and tighten all voltage sensing and power connections at the alternator terminal box and the AVR.
  • Isolate loads: Disconnect large nonlinear loads (e.g., VFDs, UPS) and observe if voltage stabilizes. If so, consider adding filters or derating the generator.
  • Governor stability: Observe engine speed/frequency. If it hunts, adjust the governor stability/damping settings according to the manual.
  • Replace AVR: If instability persists with stable speed and good connections, replace the AVR.

Persistent instability can damage sensitive equipment; consult a generator specialist if basic checks do not resolve the issue.

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Repair Difficulty

Hard 4/5

Required Part

Automatic Voltage Regulator (AVR)
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