Off the top of my head...
Blower/Resistor, both, control panel or flap motors. However if the fan will not function properly I would drop it and replace the resistor at the least and possibly both fan and resistor.
Just realized your 2012 may be slightly more complex then last model but on a e65 or e66 for example it is under the passenger side glove box area, takes 30 minutes to do. Could be in the same place, just a few screws and plugs then T20 torx's, pull tabs turns and drops out.