9 FLASH
Mighty Mule
Overvoltage or Undervoltage Protection
Opener will not start; control board LED blinks 9 times repeatedly.
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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
Line voltage outside specification, Loose power connections, Shared circuit with heavy loads, Failing power transformer on control board
How to Fix / Troubleshooting
Safety first: Only qualified persons should work inside electrical panels. If you are not comfortable, contact an electrician.
- Check outlet: Plug a lamp or tester into the opener’s outlet to confirm power is present and stable.
- Avoid shared heavy loads: Do not share the opener circuit with large appliances (air compressor, freezer, etc.) that cause voltage dips when starting.
- Inspect power cord and plug: Look for damage, burns, or loose blades. Replace the opener power cord if compromised.
- Measure voltage: With a multimeter and proper safety precautions, verify that voltage at the outlet is within the range specified in the Mighty Mule manual (typically around 120 VAC in North America).
- Internal transformer: If supply voltage is correct but the board still shows 9 flashes, the internal transformer or power supply section may be failing and the control board should be replaced.
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Repair Difficulty
Hard
4/5
Required Part
Mighty Mule Control Board
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