Whirlpool · Microwave Serious
F9 — Relay Control Board / Wiring Fault
The control could not execute the requested function — there's an issue with the appliance control board, the relay control board, or the wiring between them.
- Keep using it?
- Limited use only
- DIY difficulty
- Moderate
- Verified against
- producthelp.whirlpool.com ↗
How to fix it
- Power down at the breaker for 1 minute and retest.
- Unplug the microwave and remove the cover. Identify the relay control board (separate PCB on built-in / combo units).
- Reseat every connector at both boards and inspect for burn marks.
- Repair or replace the harness if damaged.
- If F9 returns after reseating and the harness is clean, replace the relay control board. Replace the appliance control board only if a new relay board doesn't clear it.
Why it happens
Typical signs: F9 on the display · Microwave will not start any cycle · Code returns after Cancel or power reset
- Failed relay control board Most likely on units with a separate relay board.
- Loose or burnt wiring between control and relay board Inspect the inter-board harness for melted insulation.
- Failed appliance control board Test the relay board first — usually the cheaper fix.
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.
- Whirlpool microwave relay control board Common replacementAmazon →
More Whirlpool 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: producthelp.whirlpool.com.