LG Microwave F4 Error — Keypad Short Fix Guide

What Does This Error Mean?

F4 on LG microwaves means a keypad button is reading as continuously pressed — usually because grease or food residue has trapped under it, or moisture got into the membrane.
Wipe the keypad with a damp soft cloth, dry thoroughly, and try again.
If F4 persists, the keypad membrane has failed internally — replacement is service-tech work (50–150 USD parts plus labor).

Affected Models

LG over-the-range microwave
LG countertop microwave
LG NeoChef
LG LMV series

Common Causes

Grease or food residue under a button
Moisture in the membrane after cleaning
Membrane physically damaged from sharp tools or abrasive pads
Button stuck mechanically
Membrane internally failed after years

How to Fix It

Unplug the microwave.

Pull the plug or switch the breaker off.
Wait a minute before working on the keypad.
You don't want it active during cleaning.
Wipe the keypad with a damp cloth.

Use a soft cloth slightly damp with water and a tiny amount of mild dish soap.
Wipe the entire keypad, paying attention to the edges of each button.
Don't spray cleaner directly on the keypad — moisture can seep in.
Dry thoroughly with a clean cloth.
Try each button.

Press each button individually.
If one feels mushy, stuck, or doesn't return after pressing, that's the cause.
Press it firmly several times to free it.
Sometimes a stuck button frees with a few activations.
Restore power and check.

Plug back in.
The microwave should boot normally.
Try a 30-second cook.
If F4 doesn't return, you've fixed it.
If F4 reappears, the membrane has failed internally — moisture damage may be permanent.
Schedule keypad replacement.

Most LG-authorized centers can replace the keypad membrane in one visit.
Parts run 50–150 USD depending on model.
Total bill 150–250 USD with labor.
For older microwaves, weigh against replacement cost of the whole unit.

Frequently Asked Questions

Can spilled water cause F4?

Yes — if water splashed onto the keypad while cooking and seeped through the membrane edges, it shorts the contacts.
Sometimes drying out clears the issue temporarily; the moisture damage often becomes permanent.
Wipe spills off the keypad immediately to prevent.

Is the keypad worth replacing on an old microwave?

If the microwave is under 5 years old: yes, replacement is cost-effective.
Over 7 years: probably not — newer microwaves are more efficient and usually have better feature sets.
Get the service quote, compare to the cost of a comparable new microwave, then decide.