F9 — Door switch / monitor switch fault
F9 indicates the control detects a disagreement among the door interlock switches (primary, secondary, monitor). The microwave will not start, which is a safety-critical lockout — the monitor switch exists to blow the fuse if the primary switches fail.
- Keep using it?
- Limited use only
- DIY difficulty
- Hard
- Verified against
- geappliances.com ↗
How to fix it
- Unplug the microwave — interlock work is safety-critical.
- Inspect the door for sag, loose hinges, and worn latch hooks.
- Remove the control panel / grille to access the three door switches.
- Test each switch for proper open/closed action with a multimeter, in the correct sequence as the latch operates.
- Replace any out-of-spec switch AS A SET (all three) for safety.
- Verify the latch board / switch holder is not cracked; replace if it is.
- If the line fuse has blown, replace the ceramic in-line fuse with the exact rating. If you're not comfortable with HV work, call a tech.
Why it happens
Typical signs: F9 in display · Microwave refuses to start with door closed · Display goes dead and line fuse blows when door is operated · Door feels loose or doesn't latch firmly
- Misaligned door / worn latch hooks Hooks no longer push all three switches in the correct sequence.
- Failed primary, secondary, or monitor interlock switch Any one of the three out of sync triggers F9.
- Broken door switch holder Plastic switch carrier cracks and lets a switch float.
- Wiring fault in the door switch harness Less common; inspect after switch tests.
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.
More GE microwave codes
Always unplug an appliance before servicing it. This guide is for informational purposes and is not a substitute for a qualified technician. Verified against manufacturer documentation: geappliances.com.