If your interior blower fan is cutting out randomly, check the corresponding relay. The control unit gets power through it as well. If the relay fails a chain reaction evolves. A worn relay heats up way too much when passing a high current (which is the case with a running blower motor) due to high contact resistance. The heat will melt its socket and corrode the contact pins as well as the crimping. Happened with mine a few weeks ago. Had to replace the whole socket with one from a breaker.

If your relay socket looks okay still you can open up the relay and refresh the contact surface or just replace it. For testing you could just bridge the two high current pins in the socket.

EDIT: Yes, the control unit also controls the flap which directs the air through the heater matrix.