Cats terrified of ceiling fan to the point of avoiding most of the house

My cats are usually really confident and are not scared of anything - drills, power tools, vacuum, everything is fine, so this is a new one for me. they are 4F and 3F, we just got a ceiling fan in our bedroom for the first time a week ago and since then the whole side of the apartment (the two bedrooms, the toilet and bathroom) have been classified as “no go zones”.

I know a week is a short amount of time, but I don’t see any progress at all. Instead, they are now refusing to enter the bedroom even when the fan is off. I feed them close to the bedroom, but I have to leave the bowls in a place where they don’t see the fan, otherwise they run and stay hungry.

I‘Ve moved their necessities (water fountain and litter boxes) into the “safe zone” aka the only room they will use as to not cause any health issues. But seeing them this stressed out in what’s the hottest summer on record here (France) and with another heatwave approaching, is making me worry… For those whose cats were terrified of a ceiling fan, how did you get them used to it and how long did it take?

Required info: I am the owner, not a minor, we live in France, vet is accessible but this si a behavioral issue, cats are 4F and 3F neutered, can afford the vet no problem.