Both of the ceiling vents have what appears to be the same issue. When I turn them on from the touch pads they won't go up or down UNLESS I press firmly on the knob. It's as though a keeper is loose and they need pressure on them to engage the gears that raise and lower the vents.
I have not taken the knob assembly apart yet to look; hoping someone out there can give me a heads up...?!
What coach do you have? If it is the fantastic vents they may be worn and need new motors. Only 2 screws to remove the motor gear assembly.
Checking the OP's profile page...indicates they have a 2006 Phenix.
Which I know nothing about...
Funny story when I had to work on my FF vent motor. It was in a closet over the stacked washer/dryer. Once I pulled out the screws and pulled the motor out I kinda lost my balance standing on a box (all I had at the time). Bounce, bounce, yep, right behind the dryer. I had to use a magnet taped to some sticks and finally after a couple hours got the motor out. But when I went to put the motor back in place I had taped cardboard all around so it couldn't fall again!
Murphy strikes again!
Sorry for the tardy response; been on the road. The motors seem to operate fine, but it's kinda like threads are worn and not engaging the gears...? Can't see a brand name...
You have Fantastic Fans, so you probably need one of these;
Amazon.com: Atwood (K6050-80 White Autotrol Motor with Cap-Off: Automotive (https://www.amazon.com/Atwood-K6050-80-White-Autotrol-Cap-Off/dp/B00L5HPH3C/ref=sr_1_3?ie=UTF8&qid=1540675514&sr=8-3&keywords=fantastic+fan+parts)
Sounds like what happened to mine when I "lost" the motor behind the W/D. I managed to fix it using Plast-Aid. Been a few years so I don't remember exactly whether it was the thread holes or what but the motor wasn't making good contact with the gears.