I had a sevice call from an owner that had no cooling on a 2 ton Trane XL14i (R410A) heat pump. It was determined that the compressor had gone bad because there was no pressure differential and it was only drawing 3 amps. I replaced the compressor and noticed that the suction pressure was around 50 psi and the head pressure was climbing to almost 500 psi when it finally tripped on high head. I then tested the system in heat mode and the pressures looked normal at 135 suction, 300 head. Ambient temperature was 74 DB/67WB.
I then tested the sensing bulb on the indoor TXV by placing it in warm water and switched it back to the cooling mode. The head pressure stabalized at around 250 psi. While I was testing the bulb, the outdoor unit would trip off and on, most likely on head pressure. I strapped the sensing bulb back on the suction line with insulation and closed the unit back up. I ran the system in cooling and had the same pressure readings (50 suction/500 head) until it tripped off on high head pressure.
I'm suspecting that if it is a bad TXV, this could have resulted on his compressor failing after only 3 years. Is it most likely the TXV or could it be something else?