The fan of my 27" late 2012 iMac has been making a very loud noise. I took it to an Authorized Apple Service Provider (unfortunately there're no Apple stores in Singapore, where I live). To make a long story short, the technician informed me that there is a problem with fan sensor and the solution to that is to replace the logic board, at a cost of ~$1000. This cost seems very unreasonable to me. Any advice on how much this type of thing should cost as well as about any workaround (I read somewhere that there may be ways to regulate the speed of the fan through some software addon, for example) will be greatly appreciated!