I am an hvac tech and I have a 3 ton Heatpump system that uses R410A. Unit is factory charged still and has almost exactly a 15 foot lineset. When the unit is put into heat mode it works perfect and all pressure readings are money on. When the unit is switched into cooling mode the reversing valve changes over the outdoor unit starts up the suction line starts coming down then all the sudden the liquid line pressure goes into the overpressure while the suction line goes into the negative pressure. So I am thinking restriction. I took the TXV out and opened and closed it with hot and cold water and it appears to be working and blew back threw the coil and no stoppage there. I know the txv is not used in heating mode and goes through the bypass so im still thinking txv problem. ANY suggestions from here???? Please help customer IRATE as you can imagine. Thanks, Joe
Did your hot/cold water test have an effect on the suction pressure?
A faulty metering device could cause a low suction, high discharge, high superheat, high subcooling and low compressor amps.
You most likely have 2 txv's in that heat pump system. There usually is one hiding in the outdoor unit. The txv in the outdoor unit is active in the heat cycle, so I would replace the indoor txv.
May want to look at check valves and bi-flow filter dryers. Magnets on the reversing valve to check shift positions.