1-Chemically clean and check both coils..inside and out. 2-check condition of contactor, replace if points pitted and burned. 3-Check condition of compressor windings (meg) 4-Check all safety devices operation, wiring and controls. 5-_check all low voltage wiring 6-check calibration, and if needed (mercry switch type) level of thermostat 7-Check superheat, or subcool, adjust if needed. 8-Check blower motor, and clean if needed. 9-Check system operation, delays, etc..should be done at the same time of safety system check. 10-Clean condensate drain, replace bact tabs, or sheets. If equipped with a condensate pump, check operation of float, overflow switch, check wiring condition, and remove pump and clean tray. 11-Check all duct fittings and seals. Repair as needed. 12-Check fan motors, oil if needed, or if you can as most today you cant. You dont have a belt drive unit if its that new, so no belt to worry about, but if you do, replace it even if it looks fine, oil bearing cups, oil motor, and adjust tension properly, and this means new belt, tighten, run for 20 minutes, and adjust again. 13-Check amp draw on all motors, including compressor.
VERY Basic list. Some may take more, or less All that assumes you put in a new filter too... If not, add a filter change to it.
if the company doing this states you need refrigerant, they BETTER have checked superheat, or subcool, filter condition, condition of indoor coil, blower etc...BEFORE they state this, and they BETTER use a scale like a CPS digital or the like to weigh in the charge....if not...fire them.