So we need the OP to tell us which control type his A/C has.
Doug, thanks for the explanation. Wall t'stat = freeze sensor. Two knobs like an old "window shaker" = no sensor.
I wonder about the two-year age of this A/C. Could well be time for a good cleaning of the topside unit. Evaporator Core and Drain Pan. If Chris Bryant weighs in on this, I think he'd say an Annual Cleaning is appropriate.
And! Cleaning provides a chance to see if the Freeze Sensor (given wall t'stat) is in place where it should be.
What's the correct sensor placement? Can it be tested? How?