Microwave oven exhaust fan

Sounds like the magnetron is overheating. There is an automatically-resetable thermal circuit breaker attached to the magnetron. Most likely your problem is caused by either a cooling fan that is not running, or is running too slow (caused by gummed-up bearings). In some over-the-range (OTR) microwave ovens, the exhaust fan is run at a slow speed to cool the magnetron, and if it's bearings get gummed up, it won't run on the slow speed. But if it's a new OTR microwave, then the exhaust fan may be pointing the wrong way. (It is rotatable, depending on the installation). For example, if it is pointing up, but you don't have an exhaust vent over the microwave, then the air has nowhere to go, and the magnetron will overheat.

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Go inside and check all of the connections related to the fan. Check the fuses, and the fan itself.

The inspector is correct, air should be coming through the top louvers, although you sometimes will have a little air coming from the sides and back. Drop the microwave and see which way the blower is rotated, towards the louvers or towards the back or top. Some units also have a panel that blocks the venting from going the wrong way. Good Luck, Appliance Specialists

most microwaves do not blow air out the bottom.They pull air from the bottom and blow it out the top.

Hi,

The fans on an over the stove microwave can be rotated up to 180 degrees depending on how the installer intends to vent the hood. Your fan is pointed forward and venting into the kitchen through a charcoal filter. If you want to vent through the ducting and out of the kitchen, you'll have to drop the microwave down off of the mounting bracket and rotate the fans in the back, pointing the dicsharge upward for a vertical vent, or 180 degrees, if it discharges out the back (wall vent). In both cases, an adapter is necessary, and can be obtained at any hardware store.
Best regards, --W/D--

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.

On some GE models, the turntable motor and stirrer motor are powered off a tap on the internal cooling fan motor and in such cases they will be marked "21V AC".

When I say internal cooling fan, I do not mean the hood vent exhaust fan which you can turn on and off manually.

I'm instead talking about the internal fan which comes on automatically whenever you microwave.

It is vital that the cooling fan runs, or the turntable and stirrer won't work, and magnetron will soon be destroyed.

A quick test is to remove the stirrer cover in the ceiling of the oven. The owner's manual tells you how, and you can download that here.

Then run the oven for several seconds with a cup of water inside while watching the stirrer blade in the top. It should turn very slowly.

If it does not turn or is jerky, it or the cooling fan is not working.

Also, we have a sound clip of what a microwave should sound like when the cooling fan and everything else is working here. The cooling fan's absence will be notable after you hear the clip.

The turntable system otherwise consists of the motor, the coupler, the turntable support with rollers, and the tray.

You can see and hear a video of how a turntable motor should sound when you rotate it by hand.

If the cooling fan is good, but yours won't rotate or it sounds like it's grinding, etc., you may have a bad motor or plastic coupler.

To replace either, you need to unplug power, then remove the bottom cover of the oven.

There should be a "mini-manual" (tech sheet) hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting, testing, and locating components.

At our Web site, we have a video available showing how to remove a typical over the range control panel assembly in under 5 minutes.

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

Accessing some parts may require you to pull the oven from thew wall and remove the cover.

If so, the installation instructions are very handy, and it's best to have two people since the microwave can be heavy and awkward.

You can download GE owner's manuals and installation instructions here.

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

check the control unit and high voltage circuit, and megnetron, high voltage diodes, wiring and high voltage fuse etc.,

It sounds like the bearings may be going bad on the fan motor. It's also possible that there may be sonething stuck in the the grlle or fan area, like a paper label, etc. You can find exploded views and order parts here: http://tinyurl.com/gv383 We have critical safety and disassembly help files at our site, which you can find via our listing here: http://tinyurl.com/yzjozk

"Microhood" seems to be a slang term for the "microwave hood" (hood fan or exhaust fan) which is normally part of an over-the-range microwave oven or range. But these should be available separately, as I seem to recall. I would contact home centers such as Lowe's, Home Depot (if they still exist), etc., or a local appliance store.