Fan runs by itself

My 2021 Frigidaire also turned on by itself 2 days ago. It also got hot and would not turn off except at the breaker. After 10 minutes I turned breaker on and the microwave was still on. Turned breaker on the next morning and all good. We are afraid to leave house unless we turn breaker off. Any suggestions? Do I need a new microwave?

It sounds like you understand that the exhaust fan is SUPPOSED TO come on when the microwave oven gets hot when exposed to the heat of the range below it, since you mentioned that no burners are turned on. So in that case, I'm pretty sure that you have a bad fan thermostat. It's usually located behind the control panel on the bottom (inside bottom) of the microwave floor.

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follow this steps and fix it. God bless you

1. Interlock switchIf your microwave is turning itself on, the first thing to check is the interlock switch. This is usually the first thing to malfunction that could cause this issue. If the interlock switch is bad then it will need to be replaced.
   
2. Main control boardIf your microwave is turning itself on and the interlock switch is still working, the probable cause is the main control board. If the control board is defective it will need to be replaced.
   

Read more: http://www.appliancepartspros.com/repair-help/microwave-repair-help.html#9#ixzz2aNH65mG4
http://www.appliancepartspros.com

-You're already answer yourself.


Good luck


Mai

That humming is the Magnetron turning on and off, that is what all MW oven do, it is nothing to worry about.

This sounds like a thermal protector is turning the microwave off. If I were to hazard a guess, it would be the magnetron (produces the microwaves) is overheating causing the shutdown. If the fan was not running it would create the same condition by causing the magnetron to overheat.

It could be that the fan button is sticking or a contact has welded itself closed therefore its getting power all the time.

Board needs to be replaced

Your microwave turning on by itself is a "self preservation feature" of the GE Profile Advantium and maybe some other models. Read the manual, When your over the range oven gets warm enough, for whatever reason the venting fan comes on until a satisfactory oven temperature is reached. You are not permitted to shut the vent fan off. Also it seems a temperature near room temp must be achieved before it shuts the fan motor off, it is very annoying. We had to return our Advantium because of fan noise. I configured the ovens vent fan to the recirculate direction because we do not have a vent duct that exits the house over our range. When the vent fan acting as the ovens cooling fan automatically turned on we would have to leave the house to hear each other talk. Too bad we really liked the oven other than that major problem. G-Man

Q - My microwave seems to shut off every once in a while, what might be wrong?
A - Make sure you hear the fan is still operating in your microwave. Next is to make sure the air intake grill on your microwave is not plugged up with air borne dust and dirt.
Q - The fan in my microwave oven is not running will this hurt my microwave?
A - YES, the fan cools the magnetron and electronics, take the microwave in for service, most fans are not too expensive to replace.
Q - My microwave blows the fuse inside itself as soon as I push the start button.
A - Usually a shorted high voltage capacitor...see components section.