LOAC
Briggs & Stratton
Loss of AC Sensing / No Output Detected by Controller
Controller displays LOAC or NO AC, and the generator runs but the transfer switch does not transfer the 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
Open AC sensing wires between the generator and controller, blown internal sensing fuse, miswired or failed transfer switch sensing circuit, controller input failure.
How to Fix / Troubleshooting
Safety first: Turn OFF the generator and utility main breakers. Only qualified persons should access internal wiring.
- Verify actual output: With a meter and proper PPE, start the generator in MANUAL mode and measure voltage at the generator output lugs. If normal voltage is present, the issue is with sensing, not generation.
- Inspect sensing wires: Locate the small-gauge AC sense wires from the output lugs or transfer switch back to the controller. Check for loose terminals, broken conductors, or incorrect connections.
- Check internal fuses: Some Briggs & Stratton controllers include small fuses for AC sensing circuits. Inspect and replace any blown fuses with the correct rating.
- Transfer switch sensing: In systems where the ATS provides sense signals, verify the ATS control board connections and fuses. Replace the ATS control board if it is not sending proper signals.
- Clear the code: After restoring sensing, cycle the controller to OFF then AUTO and perform a simulated outage test.
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Repair Difficulty
Hard
4/5
Required Part
AC Sensing Harness
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