Not sure which one sounds normal. Abluftventilator vs Bad-Ventilator vs Badlüfter. Or perhaps some other words. Last time I just used deepl/dictionary for another word and someone said no one uses that word except for store catalogs.
It's the fan on the wall or ceiling that ventilate the bathroom. To remove condensation after showering for example.
Context is it's broken and I need to ask the Hausmeister to call a repairman to fix it.