Seen this on a few other forums. We had done everything we could think of. Replaced water pump, flushed coolant system and had serviced, replaced the ac sensor that one guys said worked for him, nothing seemed to work. Had another problem pop up and suggested fix for that was replacing fuse #27 under the hood. Pulled out fuse #27 and it was burnt on one end but not broken. Replaced it and haven’t had the loud jet engine fan noise in 2 weeks, even with warmer weather the past three days. Good luck!