27" LED Cinema Display Fan Runs Continuously

Hello all - within the last month or so, my 27" Cinema Display has been quite noisy. The fan runs almost continuously, blowing out lightly warm air from the left side of the lower vent (nothing out the right side). The display itself does not seem to be overly warm - in fact it feels very much the same as the 27" Thunderbolt Display that sits beside it. Does anyone have any suggestions on how I can go about troubleshooting it? Thanks!