The two most reliably documented LG microwave fault indicators are F-3, a control panel error, and a door or latch error message reported when the unit cannot confirm the door is fully closed and locked. Both are more often caused by debris or a stuck component than a genuine part failure.
F-3 — control panel error
F-3 points to a problem with the control panel, most commonly a key panel that has registered as pressed (shorted) for more than 60 seconds continuously, or foreign substances — spilled liquid, grease, food residue — interfering with the touch button panel.
Door / latch error
This appears when the microwave’s safety switches cannot confirm the door is closed and locked — a required check before the magnetron is allowed to run at all. It is commonly caused by a faulty door switch, a misaligned door latch, or a damaged door seal, but very often traces back to something as simple as a tray or piece of packaging blocking the door from closing fully.
How to fix each
- For F-3, clean the keypad thoroughly
Wipe away any spilled liquid, grease or food residue from the touch button panel and the seams around individual buttons.
- Power cycle after cleaning
Unplug the microwave, wait a moment, and plug it back in to see whether the error clears.
- For a door error, check for obstructions first
Make sure no tray, packaging, or rack is blocking the door from closing fully.
- Clean the door latch and sealing area
Wipe away crumbs or grease with a soft cloth — this can prevent the door achieving a tight seal even when it looks closed.
- Open and firmly close the door a few times
This can reset the latch mechanism on its own in many cases.
If cleaning and firmly reclosing the door does not clear a door error, the individual door switches can be tested for continuity with a multimeter — any that fail need professional replacement.
When to call a technician
If F-3 continues after cleaning and a reset, or if a door error persists with no obstruction and a properly closing door, have a technician test the keypad membrane and the door switches — replacing either is a standard, well-understood repair.
Stop and call a qualified appliance technician or electrician if you find scorched or melted wiring, smell burning, see water that has reached electrical components, or if the fault returns immediately after a repair. Never bypass a safety device — thermal fuses, door interlocks and flood switches fail for a reason, and defeating one converts a broken appliance into a fire or flood risk.
