I've got a Daikin RYP100 L7V1 split wall mounted R407C system. The system has the correct weight of refrigerant. The suction pressure wont come out of a vacuum. I have tested the 4 way valve which seems ok. I changed the head of the expansion valve with another unit which was working ok and the suction pressure still pulls into a vacuum. The 4 way valve was changed recently is it possible that the heat from the valve change could have damaged the expansion valve body? Or could it be a blocked strainer? If anyone could help me please that would be great as I am stuck.