Thank you for your notice. It takes me at long time to fix this unit. I can provide more informaiton about the system. At beginning, I guess there is some air or moisture in the system. So I recover the system and recharge it. It does not help at all. I also wonder if there exists circuit blockage. I check the pressure drop in the system. The high side pressure drop (from compressor outlet to the dryer) is less than 2 bars. The pressure drop in low side (from the outlet of the TEV to the inlet of the compressor) is less than 0.25 bars. So I can conclude that there is no circuit blockage, both the condenser and the evaporator are OK. After that, I recover the system again and replace the drier and the TEV. It still does not work. At that time, I really run out of all my ideas. Based on high side and low side pressure drop, I know both the condenser and the evaporator work well. I have already replaced the drier and TEV. The only thing I did not touch is the compressor. Although I did not have any reason to replace it, it is the only thing I could do. So I replace it by a new compressor. Since the compressor is hooked in the system by thread connection, it is very simple to replace it. I do not need to touch any other parts. After replacing the compressor, the system works perfectly. Each time after recovering the system, I use high pressure nitrogen to purge the circuit for about 5 minutes.

Since I recover the system many times, and when I replace the compressor, I did not touch any other parts in the system, I believe the problem comes from the compressor.

Please let me know if any other information is needed.

Thanks
Vincent