Complete: 2 systems worked On US unit Payne split HP: HO said started freezing up about a month ago. At the HP found system a little low in refrigerant. But when I reversed to heat mode it dropped significantly. Found the outdoor piston but was barely on. Did a quick leak search and then I pumped system down and clean outdoor piston and filter and tightened nut. Pulled vacuum and added 2lbs of 410a. System is working great at this time.