KitchenAid Over-the-Range Microwave Code F9: Two boards and their wiring are suspect

What F9 means

On KitchenAid over-the-range microwave hood combinations such as the KMHS120ESS or KMHC319ESS, F9 means the appliance control board, the relay control board, or the wiring joining them may have a problem. Two boards are on the list, so testing matters. The display shows F9 and the microwave stops. Keys may not respond at all, and the display often stays locked on the code while the lamp and fan continue to run as usual.

Common causes of F9

Appliance control board that is not responding
Relay control board that is not switching loads
Wiring between the boards that has come loose

✓ One safe check you can try

1. Press Cancel and check whether the keypad responds. 2. Unplug the microwave or use the breaker for a full minute, then restore it. 3. Run a brief test with a cup of water. 4. If F9 returns, stop using the unit and book a technician.

! Why to stop there

With two boards in play, replacing the wrong one is easy.
Both boards carry mains voltage and sit behind panels on the wall-mounted unit.
We give a written price after diagnosis, with a 30-day workmanship warranty on our work.

Opening a panel yourself does not automatically cancel a manufacturer warranty, but it can cause accidental damage, and some manufacturers set their own service conditions. Check your warranty terms, or ask us, before deciding.

→Same appliance

Other Microwave codes

Probe or Insert ProbeKitchenAid Combination Microwave Message "Probe" or "Insert Probe": Seat the meat probe in its jack PUSH or PSHKitchenAid Built-In Microwave Message PUSH or PSH: The oven is waiting for Start Registration ErrorKitchenAid Over-the-Range Microwave Message "Registration Error": Check the home network and try again Sabbath, Sab, 5Ab, or 5A6KitchenAid Built-In Microwave Display Sabbath, Sab, 5Ab or 5A6: Sabbath Mode is on SEKitchenAid Over-the-Range Microwave Code SE: Keypad or user interface problem F6 E8KitchenAid Combination Microwave Code F6 E8: Manager control stopped responding Feature Not AvailableKitchenAid Built-In Microwave Message "Feature Not Available": Try again or disable power as the display directs F6 EAKitchenAid Built-In Microwave Code F6 EA: Interface control sensed over-temperature

F9F9 questions

What sets F9 apart from F9Q?

F9 names the control and relay boards. F9Q only says to reset power and watch the oven for a minute. They are separate messages. Check which one your display shows.

Is the microwave beyond saving?

Not at all. Boards are replaceable, and we confirm which one is at issue before quoting. Boards can be swapped, and we confirm which one is actually at issue before quoting you any price.

Why do you test both boards?

The listed meaning includes both, plus the wiring. Testing shows which one actually fails. A thorough test shows which board is bad, saving you from replacing both.