"Is the air conditioning system is completely dead. Then check is the thermostat knob turned to the proper setting? Is the compressor motor running? The compressor is a football-sized case with no apparent moving parts. It is located inside the air conditioner at the center. Is it humming or making any kind of continuous noise or causing the lights to dim? If it is making a continuous noise, and your air conditioner is still not cooling at all, there may be a serious problem with one or more of these areas: Compressor Condenser Evaporator These items are not user serviceable. You will need to contact a qualified appliance repair technician to repair these components. If the compressor is not running but you do have power to the air conditioner there may be a problem in one or more of these areas: Compressor Overload and/or relay Thermostat (Open thermostat) Burnt wiring Bad selector switch Capacitor "