Hi, It sounds like the logic board has failed. The spinning up could be the humidity sensor or it could be the faulty logic boards. Some systems have a wired controller if this is the issue then you can check the screen on the unit itself. In this case a new remote controller can be added. It would be interesting to know what the issue was as I appreciate you asked this question a while ago. Hope this helps, Tom.
Hi, I did a similar thing with a Mac Mini. I simply took a time machine backup and then booted to internet recovery. From there I formated each drive in disk utility separatly to break fusion. I then swapped over to the SSD. Worked fine. I hope this makes sense. Thanks, Tom.