I changed your title for more responses.
We want to try to help but we're not mind readers. More details are needed. In what conditions is this happening (outdoor temperature, HVAC settings)? Why do you want A/C when you're asking for heat? What part of the A/C is freezing (compressor itself, evaporator, condenser, pipes)? What is the A/C charge like? Does the compressor work at all?