hello. my problem sounds very, very similar to the original post, so I figured I'd reply here.

I have a KitchenAid double convection oven (model KEBC207KWH0), occasionally a loud screeching noise comes from in between the two ovens. We never use the convection ... and have confirmed that it is not spinning when the screeching noise happens.

The noise happens regardless of whether we are using the upper or lower oven. And the noise will come and go. Sometimes the noise never happens, other times it will keep going for 10-15 minutes without stopped.

it doesn't sound like a rattling or grinding noise, but more of a high pitched screeching. So I thought it wasn't the blower motor just hitting the sides or off balance, but it could be. I didn't know if it was the blower motor OR the transformer that operates the blower motord???

It definitely is coming from between the two ovens and I can see there is a blower motor down there which the schematics for the oven calls "blower motor lower".

does this "lower" blower run only when you use the lower oven OR when either oven is working?

could it be the transformer or blower motor?

I tried cleaning the top blower motor (since I can reach that without pulling the oven out), even though the noise isn't coming from the top, but it didn't seem to make a difference.

thank you in advance for your thoughts!!