I have a Magic Chef microwave MCO160UB. I was cooking on the stove (microwave wasn't on) and the fan came on as it has done before. After a few minutes, it shut off and is now completely dead. I took it down and tested the fuse and it was fine. I am wondering if a thermostat went bad. Where is it and how do you test it? Also, what is the replacement part number?

could b stat or element probly stat

many microwaves will turn the fan on or off by themselves, when there is excessive heat they kick in and attempt to clear the air (in so many words) when this happens you can not control the fan, the microwave will not respond to off commands until it has determined there is no longer a need for it.how long has it been on?is your stove on?many times smoke alarms are tied in- are they properly functioning?if all fail you may need repair -as you should be able to control this function of the device! good luck more question just ask

Sometimes that is a fan switch to turn on the blower if it gets too hot when cooking on the stove top. But you say the schematic shows it should be closed. So jump it and try the unit. if it works OK then replace it.

If you could get it to reset by unplugging it I would suspect a problem with the main timer board. A blown fuse or bad connection wont reset by unplugging it. You would need to find a parts dealer who carris Magic Chef parts and give them your model number and ask for price and availability on the main PCB the printed circuit board
( timer board)

There are typically 2 fans in these units. The fan that cools the magnetron and then the vent fan that intakes from the top of your stove then vents the air out or away from the unit. Are the lights that shine on the top of the stove working?? Sometimes if a bulb blows violently it can blow a trace off of the back of the main circuit board and that trace may also supply power to the fan

try gliding your fingers over the touch pad to see if any other buttons work , #8 is stuck, or shorted

well an educated guess would be a short or loose connection in a common thats shared between the two that could rattle loose when it so chooses.. without a wiring diagram it would be hard to guess more specifically where without laying hands upon it.. and for that you'd have to lower it to the countertop level and dismantle to test.. it could always turn out to be a bad board also, but thats usually a done deal and doesn't repair itself then break again..
best of luck,
ttfn

I have the same problem with my new magic cheff over the stove microwave oven. I call magic chef and they gave me the 800 number for the service center (1-800-775-0202). When I described the problem they told me to just put a plate under the popper and this wouldn't happen anymore. I haven't tried it yet but here's hoping.

Right, that would be MCO10UW and the owner's manual is here.

The owner's manual does say this, of course,

"To prevent overheating from taking place, the exhaust
fan is designed to automatically turn on at a low speed if
excessive temperatures occur. Should this happen, the
fan cannot be manually turned off, but it will
automatically turn off when the internal parts have
cooled. The fan may stay on for up to an hour after the
range and microwave oven controls have been turned
off."

That;'s standard on microwaves.

But these models do have a separate internal cooling fan (which should run any time you microwave) plus the hood vent exhaust fan, which should only run when you select it, or if there is an excessive stovetop or under-hood temperature.

So if it comes on whenever you microwave, that is incorrect.

When that happens, it's usually a defective vent thermal switch (a.k.a. hood TCO).

But since it's brand new, I would certainly contact Magic Chef about this. If it's in need of repair, they will fix it free, assuming the oven wasn't physically damaged.

For more help from Magic Chef / Ewave see here or their contact page.

For Magic Chef in Canada call 866.587.2002

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

Fan turned on after cooking because a thermostat got to hot and tripped turning on the fan to try to cool the unit.  The unit went completely dead when thermal fuse tripped which is located above the cavity on the left side.