F9 Serious Moderate DIY

Whirlpool Microwave F9 — Relay Control Board / Wiring Fault

Whirlpool Microwave · Error code F9

What F9 Means

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.

Symptoms

  • F9 on the display
  • Microwave will not start any cycle
  • Code returns after Cancel or power reset

Common Causes

1
Failed relay control board

Most likely on units with a separate relay board.

2
Loose or burnt wiring between control and relay board

Inspect the inter-board harness for melted insulation.

3
Failed appliance control board

Test the relay board first — usually the cheaper fix.

How to Fix It

  1. Power down at the breaker for 1 minute and retest.
  2. Unplug the microwave and remove the cover. Identify the relay control board (separate PCB on built-in / combo units).
  3. Reseat every connector at both boards and inspect for burn marks.
  4. Repair or replace the harness if damaged.
  5. 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.

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 Whirlpool microwave relay control board View on Amazon→

More Whirlpool Microwave Codes

AccuPop Fail AccuPop Fail — Popcorn Sensor Fault Demo Demo Mode — Not Heating Door Door / Open Door Closed — Safety Reminder F1E4 F1E4 — Appliance Control Board Fault F1E5 F1E5 — Inverter Internal Fault F2 F2 — Keypad / Control Fault

All Whirlpool codes → All microwave codes →

Verified against manufacturer documentation: producthelp.whirlpool.com

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