I went on a call after someone had added some r-22 to the unit. The suction was low, head was really high. The liquid line was frozen up earlier per the maintenance guy. So i thought maybe the drier was plugged. I had a temp drop across it. So i replaced it and weighed in the charge. Well i found that the unit was freezing up on the outlet of the heating TXV in the cooling mode. I do not see any external check valves or anything. The part number on the valve was a BIVE 4. I was wondering does that mean a bi flow txv? So i am assuming the txv has a internal check valve in it that allows it to be metered one way and full flow the other way, but i am not sure. Well it seems like it is metering it both ways. So i am going to change the valve tomorrow. My question is does it seem like the valve is possibly defective. I have never seen a TXVs internal check/bypass fail before. Has anyone else seen this?