LG Microwave F-7 Error: Stuck relay / welded contact (control board relay failure)
LG microwave error — here’s what you need to know. The F-7 error code on your LG microwave indicates a stuck relay or welded contact — a power-switching component on the control board is fused in the closed position. This is a High severity issue. What Does F-7 Mean on an LG Microwave? The F-7 […]
~10%
DIY Fixable
From $120
Typical Repair Cost
1.5–3 hours
Pro Repair Time
Quick Assessment
Answer to continue safely
Is it safe to keep using?
No. F-7 indicates a potentially welded relay that can allow the magnetron to operate uncontrolled. Unplug the microwave immediately and do not use it until a technician has inspected and replaced the faulty relay or control board.
Can I reset the code?
Yes. A reset will not resolve F-7. The fault is caused by a physically failed relay component that must be replaced. Resetting and reusing the appliance could create a fire or shock hazard.
When to stop immediately?
Stop if you notice: The microwave continues to operate in any way after the door is opened, You detect a burning smell, see smoke, or hear arcing sounds.
Symptoms You May Notice
Microwave continues to run after the door is opened
The most dangerous sign of a welded relay: the magnetron or interior light remains active even after the door is opened, because the stuck relay is bypassing the door interlock safety circuit.
F-7 code displayed; unit will not start
The control board has detected the stuck relay condition and locked out cooking functions, displaying F-7 as a safety intervention.
Burning smell or visible arcing from the control board area
A welding event on the relay contacts can leave a burnt electrical odour or produce audible popping/clicking from the rear of the unit where the control board is located.
Intermittent or unresponsive controls
Buttons or display elements stop responding, flicker, or behave erratically because signals between the control boards are disrupted or corrupted.
Possible Causes
Relay contacts welded by arcing
Repeated high-current switching or a voltage surge has caused the relay contact surfaces to arc and fuse together in the closed position.
Requires ProfessionalWorn relay contacts at end of service life
After many thousands of switching cycles the contact surfaces erode or pit, eventually causing them to stick together when closed.
Requires ProfessionalControl board relay driver circuit failure
The transistor or IC driving the relay coil has failed, preventing the relay from releasing its contacts even though the contacts themselves are mechanically sound.
Requires ProfessionalSafe Checks You Can Do
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1
Unplug the microwave immediately
Disconnect the microwave from the wall outlet right away. Do not attempt to restart the appliance. A welded relay is a fire hazard and the unit should remain unplugged until serviced.
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2
Check for signs of burning or arcing
With the unit unplugged, inspect the exterior vents for signs of smoke discolouration or burning smell. Document any findings for the repair technician.
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3
Do not attempt a reset
Unlike most error codes, F-7 should not be reset and retried. The fault indicates a hardware component has physically failed and cycling the power will not make the appliance safe to use.
When to Call a Professional
Contact a qualified technician if:
- F-7 is displayed — always requires professional inspection before further use
- Unit continues to run or hum after the door is opened
- Burning smell or scorch marks visible on the control board or near relay components
Need Professional Help?
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