F-5
LG · LMHM2237ST 2.2 cu. ft. Over-the-Range Microwave with EasyClean
Main control board internal fault — relay, triac, or processor/EEPROM error. Disconnect power 5 minutes. If F-5 returns, board needs replacement. If magnetron relay stuck closed, microwave could run with door open — RADIATION SAFETY HAZARD, take out of service immediately.
Error F-5 on the LG LMHM2237ST 2.2 cu. ft. Over-the-Range Microwave with EasyClean means: Control Board Error. The top-ranked community fix is “Replace the Main Control Board” (hard difficulty, ~60 min, DIY cost: $20-$30). 2 community-ranked fixes available below.
Published February 2026 · 2 fixes · microwave
Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.
While many microwave repairs can be done safely at home, consider hiring a qualified technician if:
Average professional repair cost for this issue: $200-$350.
Door Switch Failure
Exhaust Fan Motor Noise/Failure
Open Thermistor / Thermal Error
Shorted Thermistor
Touchpad Shorted Key
Humidity Sensor Error
Magnetron Failure
Sensor Error / Key Input Error
The LG LMHM2237ST 2.2 cu. ft. Over-the-Range Microwave with EasyClean has 8 other known error codes:
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