Inspected upstairs heat pump for faults. Tested refrigerant pressures in cooling and found low sub cooling value. Charged the system to achieve a 11 degree sub cooling per the system specs. Tested system is heating mode without heat strips and system shut off on error code 441, OD inverter outdoor compressor amp draw. The system runs great in cooling but fails to operate in heating leading me to believe the outdoor txv is faulty. Ordering the outdoor txv and advising a complete recovery and fresh refrigerant recharge by weight.