Carrier heat pump problem

Hey guys. 2 ton carrier heat pump r22 system is causing us some issues. On cool mode the heat pump switches to heat on its own randomly. The compressor and fan continue to run and cold air can be felt blowing out of the outside unit. I don't have gauges,so I'm limited as to what I can check. It's not my unit but I have been told in the winter it doesn't defrost mode properly. Thanks