Microwave oven fan will turn itself on and off constantly when not using the regular oven. Afraid to leave microwave plugged in because it comes on and goes off so much. Kenmore model 721.62649200

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?

Could be in one of the micro switches for the door or in the board. Most commonly one of the switches though.

It's cooking when it shouldn't, but the internal cooling fan is not running, so the magnetron is overheating, which can kill it.

Then when it gets hot enough, it trips the magnetron's thermostat, interrupting all power to the microwave. When it cools, it comes back on.

If and when an oven is coming on or doing anything by itself, this is very dangerous and can result in a fire.

So until it is repaired, please leave it unplugged or leave the door open when it's not in use, and of course one should never leave a microwave unattended while cooking.

The problem is almost certainly that the power relay on your control circuit board is shorted.

We regularly repair such control units for customers nationwide by mail for $39.95 postpaid with a one-year guarantee.

Feel free to contact me directly (and please remind me of your full model number from the tag on the unit) for more free information & help.

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

William E. Miller, AS-EET
[email protected]
http://www.microwavedisplay.com
Microwave Oven Control Panel Repair Nationwide

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

You have a shorting membrane keypad.

If and when an oven is coming on or doing anything by itself, this is very dangerous and can result in a fire.

So until it is repaired, please leave it unplugged or leave the door open when it's not in use, and of course one should never leave a microwave unattended while cooking.

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

I think the switch is stuck in on .Have you try to replace it?

This absolutely is a fire hazard.

Until it is fixed, you are right to either unplug it or simply leave the door open when you;re not using it.

You have a failed membrane keypad.

If you would like to have us to do this repair for you, we do that for $39.95 plus part costs.

Feel free to contact me directly (and please remind me of your model number) for more information & help.

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

William E. Miller
[email protected]
http://www.microwavedisplay.com

We have the same problem - auto turn-on, non-functioning keys...
I called Magic Chef and they gave me another number to call:
1-888-775-0202
I called, told the rep about our possessed microwave, and they said someone will be calling to schedule a repair visit. We bought the microwave around May '08 and it is still under warranty.
Call this number and get it fixed. It is a safety problem and Magic Chef should take care of it for you.
Brian

which fan? the exhaust fan or the control board cooling fan? the cooling fan is controlled by a thermostat just behind the control panel. it turns the fan to protect the board from overheating.