Hi all, this is my first MB. I am wondering if the heater blower is supposed to cut off completely while driving or if it just keeps blowing while the monovalve regulates the flow of hot coolant. Mine cuts off completely for a few minutes, then it comes back on again just like nothing ever happened...however, it doesn't do this 100% of the time. this morning it didn't do it at all during my 50 mile commute from work to home. Are the brushes in the blower going out or is the climate control getting finicky?

by the way, it's a 1989 190E