The most common reason an air conditioner is not cooling the air coming out is that it needs to be cleaned. If cleaning the system doesn't solve the problem, an air conditioner technician needs to come to check the refrigerant and electrical connections.
If the outdoor air intake unit is obstructed or the air filter is dirty, the air conditioner cannot cool the refrigerant that is used to cool the air in the home. Before you start, turn the power off to the air conditioner unit by turning the switch at the electrical panel.
Clear away large debris from the outdoor unit that might be blocking the intake. Next, remove the grilles from the unit, and use a vacuum with a brush attachment to clear away dust and dirt. Finally, use a hose to spray away remaining debris from the inside of the grilles and then replace them on the unit. To test to see if the unit is working properly, turn the thermostat to OFF, switch the air conditioner back on at the electrical panel, and then turn the thermostat back to ON.
If cleaning the air conditioner doesn't solve the problem, call an air conditioner technician to diagnose and repair the problem. A technician is also able to clean the system properly and thoroughly if necessary.