There are many reasons which might contribute to the air conditioner not blowing cold air. Before contacting a professional, you can try some of these things and see the results. Clean the dirty air filters and, if required, change the same. Make sure that the thermostat is set correctly at the right temperature. There might be a leak in the ductwork from where cold air is escaping. Low levels of refrigerant/coolant are also a probable reason for the air conditioner not blowing cold air. Seek professional assistance from a reliable AC repair and servicing company if the problem persists for long.