I am having an issue with my 2014 BMW 640i Gran Coupe x Drive just recently; every time when I turn on the heater this odd and very loud sound from the fan comes on and its non stop. It gets even louder the longer I leave the heater on. However the moment I turn off the heater, or simply turn on the A/C the noise of the fan turns off. Can this be a DIY solution or pro? Any suggestions on what it could be would be greatly appreciated! Here is a video of the sound its making: https://www.youtube.com/watch?v=wGpiKtAk7XM