Before I dismantle the whole thing, I thought I would ask for any pointers....

There is a fan noise (?) when the microwave is on. It is working otherwise and the turntable is working. I took off the assy. grill and the filter too see if I could pinpoint the sound. I see in the parts list that there is a ventilation motor assembly and also a fan motor assembly. The question I have is..the ventilation motor has two things that turn and neither are turning. Are any of these supposed to turn when the unit first turns on or do they come on by thermostat? Since I can't see the fan motor assembly, I assume that is on all the time. I will check both when I open it but I was just curious...

Thanks, Chris