F-3 Moderate Moderate DIY

LG Microwave F-3 — Key short / specific button stuck

LG Microwave · Error code F-3

What F-3 Means

Similar to F-2, but the control has identified a specific key as stuck closed. Often appears immediately after a spill or steam exposure.

Symptoms

  • F-3 on display at power-up
  • One button always seems pressed
  • No response to other keys

Common Causes

1
Liquid intrusion under keypad

Soup or steam wicked under the membrane during a previous cook.

2
Physical damage to membrane

Cracked overlay holding a contact closed.

3
Sticky residue under the overlay

Cleaning product or food sugar bridging contacts.

4
Failed control board scan line

PCB falsely reads a key as closed.

How to Fix It

  1. Unplug for 10 minutes to dry out condensation.
  2. Inspect the membrane for bubbles, soft spots, or stuck buttons.
  3. Disconnect the keypad ribbon at the control board and restore power. If F-3 clears, replace the keypad. If F-3 persists, replace the control board.
  4. Never use saturated rags on the panel — wipe with a barely damp microfiber.
  5. Replace the touch panel assembly if confirmed faulty.
  6. Test all buttons after reassembly.

Parts You May Need

If diagnosis points to a failed part, these are the common replacements. As an Amazon Associate we earn from qualifying purchases.

Common replacement LG microwave touch panel View on Amazon→ Common replacement LG microwave main control board View on Amazon→

More LG Microwave Codes

CH CH / Child Lock — Control locked DOOR DOOR / Door Error — Door switch / interlock fault EE EE — EEPROM / control memory error F-1 F-1 — Oven sensor open / thermistor fault F-2 F-2 — Keypad / touch panel shorted F-4 F-4 — Humidity / steam sensor fault

All LG codes → All microwave codes →

Verified against manufacturer documentation: lg.com

Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician.