I have a GE Profile Space Maker microwave with a few issues. Mainly, if I cook something like a frozen dinner that needs to cook a while (10+ minutes) a loud fan comes on and runs for quite a while.

Also, although it hasn't happened recently, occasionally it use to make a grinding sound even when it wasn't in use, and you had to open the door to turn stop that grinding.

I took the microwave out and the cover off. The vent fan seems to work, but occasionally, it would not turn on high, but it is now doing that usually. The microwave never seemed to draw steam/smoke from the stovetop cooking area and vent it out the top.