"Fans" breaker on the 12 volt panel, 47 SC
 

Probably a stupid question but the 12 volt breaker panel located in the cabin has a breaker labeled "Fans". Switched it on & can hear what sounds like a bilge blower but it is in the wall behind the bathroom. It's not the bilge blower, it's not related to the air conditioning nor is it the bathroom exhaust fan. Cannot find or feel air coming out anywhere.
Any ideas ? Thanx in advance.