Frigidaire · Microwave Serious
F9 — Door switch / monitor switch fault
F9 indicates the control sees a mismatch between the primary, secondary, and monitor door switches. This is a safety-critical fault — the microwave will not start until resolved.
- Keep using it?
- Limited use only
- DIY difficulty
- Hard
- Verified against
- frigidaire.com ↗
How to fix it
- Unplug the microwave.
- Open and close the door slowly — watch/listen for clean click of all three switches.
- Remove the control panel/grille; ohms-test each interlock for proper open/close with door action.
- Replace any switch that does not actuate cleanly.
- Check the inline ceramic line fuse — if blown, replace it AND replace all three door switches as a set (monitor trip damages them).
- Verify door alignment and latch hook engagement; adjust hinges if needed.
Why it happens
Typical signs: F9 on display · Microwave will not start with door closed · Display reads PF/F9 after door slam · Blown line fuse in some cases
- Failed interlock or monitor switch One of three switches stuck open or closed.
- Bent door / misaligned latch Hinge sag prevents simultaneous switch actuation.
- Blown line fuse (after monitor trip) A primary stuck closed when door opened blows the line fuse — replace switches AND fuse.
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 Frigidaire 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: frigidaire.com.