This solved my problem, only took less than 1 minute
The first thing you should try is reset the SMC . All you have to do is unplug the computer from the power source ( back of the computer power cord) wait 15 to 25 seconds just in case you count to fast.Then Plug it back in and RESTART the computer the fan should reset back to normal. If this trick does not work then the fan is probably dirty and needs to be cleaned or it may need to be replaced. ( Always Try the simple things first ) like going to ifixit.com and ask a question.