* Check if the power cord is damaged
* Unplug the unit for 1 minute and plug back in – Reset
* Check with the different wall outlet
* Check with the temperature set at least 3 degrees above current room temperature
* Check if the temperature properly set by the remote control . ( If the unit has a remote)
* Check if the windows and doors are properly closed
* Check if the ventilation fan has stopped
* Check if there any objects blocking the air inlet or outlet of the indoor/outdoor unit