RV Repair: Duo-Therm Air Conditioner, duo therm air conditioner, mid way

Question
I have a Trail-lite with a Duo-Therm Air Conditioner and it keeps freezing up. The Fan and heater work fine. The  unit is only 2 and 1/2 years old.

Answer
If the outside temperature drops below 75 degrees, set the thermostat mid way between warmer and cooler.  Humidity will also cause the unit to "ice up" and all you can do is turn it off, allow it to defrost before turning it back on.
Another possibility, blockage of air or bent cooling fins.  Make sure the evaporator fins are clean and unrestricted.