Tech arrived on site. Began tune up of unit. Found filter extremely restricted. Replaced with customer supplied filter. Checked indoor motor and airflow. It was good. Ducts are old and dusty. No duck leakage seen at this time. Outdoor coil was hammered. Mostly with dog hair. Cleaned coils and electrical. Checked charge. It was low at this time. Did leak detection in evaporator coil. Could not find anything at this time. Got authorization from management to fill up unit with 1lbs of r410a. Management also said they will extend parts warranty of evap coil until our next visit. On our next visit, we will need to do an isolation test to confirm where the leak is.