I have a KitchenAid KHMC107EBL microwave that the microwave portion has stopped working. The fan lights and convection still works. The microwave function give s the appearance that its in operation clock counts down and you hear what appears to sound like normal hummm but will not heat a measuring cup of water

A loud humming noise in microwave mode will usually be a shorted high voltage diode or bad magnetron.

either the circulation fan that cools the magnatron is bad,or the magnatron is bad itself.

It may be a bad door switch or mount.
(Anybody in the home opening the door while it's cooking?)
See our help file on door switches here.

common problem with lots of MWs - the door switches are not set and secured properly. Now they are totally off. Need to pull apart and reset. Not a task for an average homeowner. Mine (Whirlpool) did that 1 week after I got it - exchanged for a new one.

i have the same problem.. with the start button, could you resolve yours?

your problem is more then likely the fuse, but the fuse holder is most likely bad as well

Most likely needs a new magnetron

You have a shorted grille relay on your control board. I can repair this for $69.95, which includes insured return shipping.
For details and more free DIY and other help & advice, feel free to contact me.

William E. Miller, AS-EET
[email protected]
http://www.microwavecontrol.com
Microwave Oven Control Panel Repair Nationwide
"Recycling by repairing since 1982"

I would recommend changing the diodes as well. This will usually take care of the problem.

Sounds like a classic bad door switch or switch holder. If you or a friend decide to work on it, we have *critical* safety info, info on door switch testing and replacement, and oven disassembly info at our site, which is linked at our listing here on FixYa: http://tinyurl.com/yzjozk You can find helpful exploded view diagrams and order parts by entering your base model number (without the suffix) here: http://tinyurl.com/gv383