Upon arriving I greeted the tenants and began my work. The Delta T was -9° which is not going cool the house. After further inspection of airflow and refrigerant I found the 2nd floor unit had half of the refrigerant it should have. The first floor unit was also low but not to that degree. The homeowner approved charging the system to the manufactures specifications. He also approved for us to come back and do a leak search. No date was promised. System is operating as it should.