UNDERFREQUENCY
Guardian
Engine Running Below Rated Speed
Generator runs but controller displays UNDERFREQUENCY or LOW HZ; connected loads may experience dimming lights or sluggish motors.
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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
Excessive electrical load on generator, Governor out of adjustment, Partially blocked fuel system, Weak ignition or misfire
How to Fix / Troubleshooting
Safety first: Open the generator main breaker to remove load, then place the controller in OFF before inspection.
- Reduce load: Verify that the total connected load does not exceed the Guardian generator's rated kW. Turn off large non-essential loads (HVAC, water heaters) and retest.
- Inspect fuel system: Check for kinks or restrictions in the fuel line and ensure adequate gas pressure. Replace clogged fuel filters.
- Check air filter and spark plugs: Replace a dirty air filter and worn spark plugs to restore full engine power.
- Governor linkage: Inspect the mechanical governor linkage for binding or looseness. Do not adjust governor speed without a frequency meter; improper adjustment can damage equipment.
- Professional adjustment: If UNDERFREQUENCY continues with normal load, have a Guardian technician adjust the governor and verify fuel supply and ignition performance.
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Repair Difficulty
Hard
4/5
Required Part
Governor Linkage Assembly
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