F18
JennAir
Low-Voltage Power Supply Error
JennAir microwave displays F18 and may not accept input or may randomly reset.
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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 low-voltage transformer on control board, Shorted component on UI board, Loose low-voltage harness, Power surge damage
How to Fix / Troubleshooting
Safety First: Unplug the microwave before removing the control panel or cover.
- Check power source: Confirm the outlet is properly grounded and not shared with heavy loads that cause voltage drops.
- Inspect control board: Remove the control panel and inspect the electronic control board for burned components or bulging capacitors in the low-voltage section.
- Check harnesses: Ensure all low-voltage connectors between the control board and UI are secure.
- Replace control board: If there is visible damage or F18 persists after reseating connectors, replace the electronic control board. If the UI board shows damage, replace it as well.
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Repair Difficulty
Hard
4/5
Required Part
Electronic Control Board
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