FIXED: Computer Fan Constantly Running
In this video I share how I fixed my issue of my fan constantly running on my laptop. Be sure to try other options before resetting your SMC, but if all else fails this may be what you need to do. I didn't mention this in the video, but you may also have a build up of dust that needs to be cleared. Check out this page for other options and the directions for resetting you SMC.
https://support.apple.com/en-us/HT201295
Let me know what works for you.