Stepper motor for HVAC system question

[bmwpower]

Is the stepper motor located at #3 in this picture supposed to turn 360 degrees? There is NO #6 motor on my E34 535i. It appears mine DOES turn 360 degrees has therefore has broken the mount, cracked the heater box and the actuator rod has popped off (due to no clearance for the revolution). I've gone thru the documentation and fixes for the mount, but I didn't see a mention of whether or not the motor is supposed to turn 360 degrees.

I've been watching the motor movements (since I had to change out my heater core) and it does a couple of things:

(1) rotates 120 degress when I turn the ignition on
(2) rotates another 120 degrees when I turn the ignition off and then back on again
(3) this cycle continues no matter how many times the iginiton is turned on
(4) with the car on and the defrost vent opened, the motor turns 120 degrees
(5) with the car on and the defrost vent closed, the motor turns BACK 120degrees, back to the origin in #4 (ie, never making a revolution).

So my question is, is this motor supposed to turn 360 degrees?

Thanks!