I have a Trane heat pump unit (3 ton) that the electronic txv shuts down to the point it causes the coil to ice up. It was installed 3 months ago and worked fine until 2 days ago. The board is indicating low super heat or a stuck valve. I can cycle the power and it runs great for a day and then stops cooling yet the compressor sitll runs at 50 suction and 300 head. The system is 410. Any suggestions? All pressures are good during normal operation.