iMac fan constantly runs at full blast

I recently got a 21.5" Mid 2010 iMac from eBay, and in the listing it stated that one of the fans constantly runs at full blast. When I use the iMac, the fan starts at 100% as soon as the chime plays and it stays at 100%. I tried resetting SMC and any other generic fixes that I could find on google. Is there anything else I should try or should I just live with it?