I hope to get some ideas on a problem with my Water Furnace heat pump. It's a fresh water well system. About a year ago I had a failure in the coaxial coil and the unit lost all its gas and the refridgeration system may have been contaminated with water. Anyway I had the coil replaced and the unit evacuated and recharged with R22. A new drier also. The problem I have had ever since the repair is that the unit runs fine on cooling but in the heating mode the longer the unit runs the low and high side pressure will gradually decrease and the compressor will start to show ice on the outside and the heat output drops and eventually the unit will trip on low suction pressure. The low side pressure also hunts on the way down. All I have to do at this point is to run the unit in cooling for about 10 minutes and then back to heat and it u=runs fine for a while. What I have been doing now for the last week or so is I have put a 100 watt light bulb inside the unit right next to the TXV to keep it warm and the unit runs like a champ in heat mode. Subcooling, superheat, and pressures are right on the money according to the factory specs. Could the issue be ice forming in the TXV? My opinion is that the mechanics that did the repair may not have pulled a proper vacuum on the system. I'm EPA certified now and can do the work my self. Any ideas would be appreciated.