The fantastic vent fan in the bedroom has a problem.

On a hunch something is on the rain sensor.. Like a bird dropping.. or something both conductive and sticky (Tree Sap?) Option 2 is a short on the sensor lead. Option 3 is a bad control board. Option 4 is a stuck relay on the sensor board.

Oh and if there is an OPEN/Close switch.. that's about the list I think.

There should be a mechanical end switch that engages when the dome is closed. I had a corrosion problem there once, but on a less sophisticated Fantastic Fan model.

I believe the small motor that opens/closes the lid stops itself based on current draw. I would remove the crank handle and inspect the splines and gear box. It may also be the control board,

I think I have found the problem. When the dome is 90 to 95% close the automatic versus manual crank pops out about 1/16 to 1/8 of an inch from the automatic position to the manual position. The dome stopped moving in the motor continues to run. If I push the crank fully up into the automatic position the dome closes and the motor stops

I do not know if the motor splines are stripped or not.I need to do some more experimenting to see what causes this problem. But as of now I have a solution to the problem

Update: I do not think (?) the splines are stripped. I think the lift motor has broken free from the white plastic housing that holds it. Only two small plastic tabs that were melted in place to hold the motor. I have ordered a new motor from Amazon. AND I have attempted to glue the lift motor back into the white plastic housings. This way I will have a backup.

Sounds like you found it.. I don't like glue when I can use bolts (But since my FF was 100% manual I don't know if you can bolt it down)

Alas I have done a lot of things like that however.

If you have a speeding iron, you can use it for diy plastic welding and melt the tabs and secure the lift motor, you can use zip Ty's as plastic welding rod material