Controller displays “Overvoltage” and opens the main line circuit breaker; generator stops supplying power.

Safety first: Turn the generator OFF, open the main breaker to isolate from the building, and disconnect battery negative. Do not operate the unit with an overvoltage condition as it can damage connected loads.

• Visual inspection: Remove the alternator and control panel covers. Inspect the voltage regulator module and wiring harness for burnt components, discoloration, or loose connectors.
• Check sensing leads: Trace the voltage sensing wires from the alternator output terminals to the controller/AVR. Tighten any loose terminal screws and clean corroded connections.
• Inspect neutral and ground: Ensure the neutral and ground connections at the generator output lugs and within the control box are tight and not overheated.
• Controller settings: On models with programmable controllers (e.g., RDC2, DC2), verify that the nominal voltage setting matches the installation (120/240 V single-phase, 120/208 V three-phase, etc.). Do not change settings unless you are certain of the system configuration.
• Test run with meter: With a qualified person and proper PPE, reconnect battery, start the generator with the main breaker still open, and measure line-to-line and line-to-neutral voltage with a true RMS meter. If voltage is significantly above spec, shut down and replace the AVR.

Because overvoltage can be hazardous, if you are not experienced with live electrical testing, contact a Kohler-authorized service provider to diagnose and replace the voltage regulator or alternator components.