Seat Ibiza car a/c and fan blowing in damp air. it has been checked for leaks and none found nor it it losing water/coolant.

If its stuck you are just recirculating the damp air already inside , Would also check / replace the cabin filter if needed .

" You should avoid using the recirculation button in the winter or in cold weather. It traps humidity inside the car, causing foggy windows and mugginess. Instead, use “Fresh Air” mode in the winter. ... This will help to flush out all the stuffy air that builds up in your car when sitting in the sun or a hot garage. "

If you run your air con it actually conditions the air and helps with moisture,just make sure your drain for ac is running out the bottom of the car,and of course as suggested fresh air rather than recycled

Most cars nowadays have a sensor that kicks the aircon on automatically to improve and quicken clearing the screen