The air conditioner has poor performance, what should I check?

1. Check for dirty air filters. Dirty filters of the indoor unit, result in reduced circulation of the air and therefore poor performance in cooling or heating.
2. Check the temperature settings on the remote control, if it is the proper according to the season.
3. Check if sleep or quiet mode has been chosen, when the fan operates at low speed and therefore the capacity in cooling or heating is significantly reduced.
4. Maybe the capacity of the installed unit is smaller than the needs of the room (with doors and windows closed).
5. The outdoor unit might be dirty or the circulation of the ventilation air is being obstructed.