Service diagnostic found that the system was low on refrigerant. I performed a leak check and did not find a leak in the system. Options for repair were presented to the homeowner and he chose to have the system charged with refrigerant and to sign up for maintenance. I added 2.5 lbs of R410A to the system and brought the system up to the manufacturer specification of 8 degrees of sub cooling. The system was running at the completion of service.