LOF
Briggs & Stratton
Loss of Frequency / Loss of Engine Speed Signal
Controller displays LOF and generator shuts down or will not start.
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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
Failed engine speed sensor (magnetic pickup), Broken or loose speed sensor wiring, Controller input circuit failure, Damaged flywheel teeth at pickup location
How to Fix / Troubleshooting
Safety first: Disable automatic start and disconnect battery negative before working near the flywheel.
- Locate speed sensor: Find the magnetic pickup or Hall-effect sensor near the flywheel or ring gear. Inspect for physical damage or metal debris on the sensor tip.
- Check wiring: Follow the sensor harness back to the controller. Look for chafed insulation, loose connectors, or pulled pins. Repair or replace damaged wiring.
- Sensor gap: If adjustable, verify the air gap between the sensor and flywheel teeth matches Briggs & Stratton specifications (often around 0.020–0.040 in). Adjust as needed.
- Replace sensor if needed: If wiring and gap are correct but LOF persists, replace the engine speed sensor with the correct Briggs & Stratton part.
- Clear the code: Reconnect battery, cycle controller to OFF then AUTO, and test start.
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Repair Difficulty
Hard
4/5
Required Part
Engine Speed Sensor (Magnetic Pickup)
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