Controller shows F12 Frequency Out of Range; generator may not transfer to load.

Safety first: Keep the generator isolated from the load while frequency is unstable. Open the output breaker and ATS.

• Measure frequency: With the generator running unloaded, measure output frequency with a meter. Compare to the rated frequency (50 or 60 Hz).
• Check engine speed: If frequency is low or high, inspect the throttle stop and governor linkage. Ensure nothing is obstructing movement. For mechanical governors, adjust the speed screw slightly to bring RPM into spec, following the Siemens service manual.
• Inspect speed sensor: Verify the speed sensor is secure and its connector is clean. Replace the sensor if the controller shows erratic RPM readings.
• Verify controller settings: In the Siemens controller configuration, confirm that the correct rated frequency and number of poles are selected. Incorrect settings can cause false F12 alarms.
• Governor module service: If mechanical adjustments and sensor checks do not stabilize frequency, the electronic governor module may be defective and should be replaced by a technician.