Microwave runs for 5 seconds then shuts down displaying F9 HELP

Step 1:

Door Switch

If the microwave runs for a few seconds and then shuts off, a door switch might have failed intermittently. Check each of the door switches for any signs of overheating, arcing, or burning. Also check each of them for continuity. Replace any of the switches that is visibly damaged or that only has continuity intermittently

Step 2:

Main Control Board

If the microwave runs for a few seconds and stops there may be a short circuit in the main control board. Check other components first, these boards are often misdiagnosed.

Touchpad and Control Panel

If the microwave runs for a few seconds and stops the touchpad and control panel might be defective. There are several other components that can cause this problem, be sure to check any other components before replacing this board.

Touchpad

If the microwave runs for a few seconds and stops the touchpad might be at fault. This is not common. Generally speaking, if the microwave display is working and some of the buttons respond correctly but some don't, the problem is with the touchpad.

High Voltage Transformer

If the microwave runs for a few seconds and stops the high voltage transformer might have an intermittent short. This is not common. Check other components related to the microwave symptom first.

Thermostat

If the microwave runs for a few seconds and stops the thermostat might be defective. Watch our video on testing thermostat

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Step 6:

use the DVOM tester and fix it. God bless you

LG's service manual troubleshooting section suggests the F9 code could be due to line voltage, magnetron, inverter module, "Relay 2", or a loose connection between door/magnetron/control PCB (Power Control Board).

Other indications might help narrow down these choices before having to pull out your multimeter and crack open the microwave case; for example, if the microwave works, but heats slowly, then the troubleshooting manual narrows your choices down to magnetron or line voltage problems, and pretty much rules out the other possiblities.

In other cases, F9 error code indicates an inverter failure. This can sometimes by caused by a power surge or glitch through the electrical lines. You can sometimes clear this fault by completely unplugging the microwave for 1 minute. Plug it back in and see if the fault code returns. If it does, then you have an internal component failure that will need to be serviced by a technician.

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You didn't mention your brand or model, but F9 code on an LG sometimes means either a bad door switch or a loose door switch mount.

See this file on door switches.

If a switch is all you need, we offer a universal type for only $5 postpaid which you can order here.

Here is more info on F9 as it relates to some brands and models:

Sears Kenmore Whierlpool LG 721.63683300

"F-9 on this microwave IS inverter related. There is a service tech troubleshooting document stuffed in behind the control board cover which has some testing proceedures. My problem was the magnatron and checked out bad with the help of this document. It would run for a few seconds making clicks and then say F-9. It has been working great since I replaced the magnatron PN 6324w1a002c."

"f9 model 721.63764300
Kenmore Elite 36 " over tne counter microwave is supplied by LG made by Gold Star, made in China. It's main problem is the high voltage inverter board supplyed by Sears Parts. If you get a F-9 code on your microwave display screen and the micro quits it's probably this board. Reset the machine by pulling the power plug and waiting an hour. If it is the high voltage board is at fault it will probably fail after 45 seconds of start up. This part is really hard to get at but is less than $100. A qualified technician should be able to remove and repair this item in less than hour. Some techs will quote you $300 labor, don't buy it, it should cost a $100 or less. No need to buy another microwave."

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

See this FixYa solution.

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

F9 indicates a problem with the door latch.  There is a safety switch that will not allow the microwave to operate if it detects the door is not closed properly.  Even though physically it may seem the door is shut, the safety switch is not relaying the message to the onboard computer.  You need another door latch switch.

This sounds like the unit is defective and if I were you I would return for replacment!

your magnatron sounds like its going out...it may be cheaper to buy a new one...hope this helps!

F9 code means either a bad door switch or a loose door switch mount.

If you or someone you know decide to look into it, we have critical safety information, info on door switch diagnosis and replacement, and disassembly information at our site, and our link is at our listing here on FixYa.

You can usually find helpful exploded view diagrams and order parts by entering your full model number here.

(If not, please reply back with your brand and model number so we can help you.)

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

If this is a "SmartWave" branded microwave oven then F9 is an error that indicates an inverter board or magnetron has failed. Either way.. Try this...With the F9 error cleared, start the oven and listen for a ticking sound. The inverter will attempt to 'fire' the magnetron 5 times.(ticking sound). If can hear ticking, replace magnetron....Else in may be a door switch problem