If the air-conditioner will not turn on: The most common cause is a blown circuit or fuse, or an improperly set or faulty thermostat. Also, many units have an internal switch that could have shut itself off.
• Make sure the thermostat is set to “cool”, not ‘Off” or “Heat”.
• Make sure the thermostat is set below the room’s current temperature.
• Check your circuit breaker or fuse box to see if the breaker is in the “On” position and that no fuses are blown.
Poor air flow inside the vents: The most common causes are a dirty air filter, blocked ducts, damage to the unit by drilled holes or punctures, or disconnected ducts.
• Confirm the air filter is clean. If it looks dirty, clean or replace it.
• Visually inspect the the ductwork as best you can to see if there are any damages or disconnections, or a dust buildup. Some areas may be difficult to reach and require the assistance of a professional.
• Make sure the vent registers are in the open position and are free of dust and debris.
Unit does not dehumidify adequately: If it is a new system, it may be that the air-conditioning system is too large for the house. An overly large system will cool the air so fast that not enough humid air will have made its way across the cooling coil to get dehumidified adequately.
• The best solution is to replace the condensing unit and coils with a properly sized system.
• Alternatively, you can run ductwork to additional parts of the house, such as the garage or basement, to increase the cooling load.