Customer stated that AC had not been coming on. Found temperature sensor reading 15 degrees in 71 degree ambient room. Batteries were in backwards. Placed t-stat batteries in correct position which corrected the issue. Performed clean and check on AC system. Changed filter that customer provided, tested and inspected blower motor assembly and all electrical components, measured delta-t, cleaned condenser coil, checked refrigerant pressures and sub cooling, checked condensate drain for proper drainage. Everything is operating normally at this time.