Have gone through entire system, verifying and calibration of airflow, ensuring static pressures are good, performed leak check, checked amp draws (compressor had slightly high amp draws), superheat and subcool are fine. However unit has consistently low suction pressure. Suspected bad practices in regards to install of unit and replacement of compressor several years ago. No other apparent problems. Will inform customer to keep home warmer than 71 at night to prevent freeze up. Leaving estimates.