- Appliances
- Microwave ovens
F9
Whirlpool F9 on a microwave: control and relay board fault
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On a Whirlpool over-the-range microwave, F9 means the oven could not execute the function, with a possible problem in the control board, the relay board or the wiring. Whirlpool says to switch the breaker off one minute and test.
Safety first
Stop and check this first
- An over-the-range microwave is not taken apart to check boards or wires: the high voltage capacitor can keep a lethal charge even with the power off. Magnetron, door seals and safety interlocks are for authorised service only.
Safe checks you can perform
- When and with which function
- Breaker off for one minute
- Normal test with a load
Leave these tasks to a qualified professional
- Do not attempt this professional task: Full test after the repair
- Do not attempt this professional task: Diagnosis of both boards and wiring
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Full test after the repair
What they doThe technician switches the unit off and on and tests all functions with a load.
They must show youthe functions running without F9.
In writingthe test, the result and the date.
Diagnosis of both boards and wiring
What they doThe authorised technician checks the signals between the control board and the relay board and the wiring joining them, with the service manual and after discharging high voltage.
They must show youthe test that rules out the other two causes before replacing anything.
In writingwhat was ruled out, what was replaced, its part number and the reason.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
When and with which function
- Who:
- you, no tools.
- How:
- note which function you asked for and whether F9 appeared on pressing Start, during the cycle or at power-up.
- Result that matters:
- when and with which function the code appears.
- If always with the same function:
- note it for the technician.
- If with any function or at power-up:
- note it; it points more to the control board or wiring.
- Evidence to keep:
- note of the function and moment, and a photo of the display.
Evidence: F9 - Error Code - Over-the-Range Microwave
Breaker off for one minute
- Who:
- you, at the breaker panel and without opening the unit.
- How:
- switch the microwave's breaker or breakers off for one minute, switch them back on and watch the display for another minute, as Whirlpool says.
- Result that matters:
- whether F9 reappears within that minute.
- If it does not return:
- test the function that gave the code.
- If it returns:
- with three possible origins, do not keep trying; ask for Whirlpool service.
- Evidence to keep:
- time of the cut and whether the code came back during the minute.
Evidence: F9 - Error Code - Over-the-Range Microwave
Normal test with a load
- Who:
- you, with a microwave-safe container of water.
- How:
- place a microwave-safe container of water inside and set a short cycle with the usual function. Do not run it empty.
- Result that matters:
- that the cycle runs to the end without F9.
- If it does:
- solved; note it if it repeats.
- If F9 returns:
- call service with your notes.
- Evidence to keep:
- note of the cycle and the result.
Evidence: F9 - Error Code - Over-the-Range Microwave
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Appliances
- Brand
- Whirlpool
- Product type
- Microwave ovens
Known code variants
- cocina LG F9
- F-9
- LG F-9 horno
- LG F9 error oven
- LG F9 horno
- LG horno F9 no calienta
- LG oven F-9
- LG oven F9 not heating
- LG range F9
- microondas Whirlpool F9 placa
- Whirlpool F9 over the range
- Whirlpool microondas F9
- Whirlpool microwave F9
- Whirlpool microwave F9 control board
- Whirlpool over the range F9
What it means
Whirlpool defines F9 as the oven could not execute the function, and widens the possible causes to three: the appliance control board, the relay control board or the associated wiring. In other words, the fault can be in either board or in the wire joining them. With three possible origins, the code is not enough to decide which part to replace; measuring is needed. The page is Whirlpool US's over-the-range microwave guide; confirm the code in your model's manual.
Warnings and stop conditions
- Higheditorial warning
An over-the-range microwave is not taken apart to check boards or wires: the high voltage capacitor can keep a lethal charge even with the power off. Magnetron, door seals and safety interlocks are for authorised service only.
Evidence: F9 - Error Code - Over-the-Range Microwave
Symptoms and causes
Probable causes · in order
- Appliance control boardPossible
Whirlpool includes it among the origins. It fits if F9 appears with different functions and returns after the reset.
Evidence: F9 - Error Code - Over-the-Range Microwave
- Relay control boardPossible
Also cited by Whirlpool. It fits if the same function always fails, although only the technician can confirm it by measuring.
Evidence: F9 - Error Code - Over-the-Range Microwave
- Wiring between boardsPossible
The third origin Whirlpool mentions. A loose connector produces the same code with both boards healthy.
Evidence: F9 - Error Code - Over-the-Range Microwave
Virtual technician
Does F9 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
F9 - Error Code - Over-the-Range Microwave
Whirlpool · 2026 · official_doc
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