Performed ac maintenance on electric roof top package unit. Went thru system first for heater to warm up house, cooler morning... then tested ac. System is from 1977. It is working for now just not running as good or efficient as it could be. Blower has a slight wiggle and vibration. All parts are working for now. Due to age of system want to watch how much money you put into system for return on investment. Change filter more often. Electrical connections ok at this time. Refrigerant ok at this time.