Performed AC maintenance.. Checked ducting for proper airflow and make sure everything was connected properly. Tested capacitor it is within range system is cooling at a 20° split. Cleaned outdoor condenser coils and removed to breathe from bottom of the condenser unit. Inspected filter does not need to be changed at this time. Inspected system for proper safety components. System does have drain pan and flood protection. Condensate lines are clear. System is cooling and operational upon departure. Customer did mention that there was a light rattling noise coming from the return. I did inspect the return and the rattling noise lessened.