There are several reasons why your AC may be blowing hot air. The thermostat is a good place to start looking for the culprit. It sounds too simple. This is a common reason why your air conditioner might be doing the opposite of what it should. Low refrigerant can cause your air conditioner to only blow hot air. Do not attempt to fix this yourself. Coolants, also known as refrigerants, can be very dangerous. To purchase and handle this substance, you must be a licensed HVAC technician. Your HVAC system’s air filters may seem unimportant, but they are essential. HVAC filters remove dust, dander, and other airborne contaminants from the air reentering your home from the system. Over time, the debris that’s caught will clog up your air filters. When this happens, your air conditioner will struggle to push air past the filter into the system. This strain can lessen air flow and even cause your system to blow warm air instead of cool. Take a peek at your filters, and if they’re dirty, replace them to see if it makes a difference in airflow and temperature. Frozen evaporator coils can cause your system to blow hot air as well. Some things which can be preventing airflow to the evaporator coil include blocked air ducts, a dirty coil, or low refrigerant. If you find your system frozen over, turn off your air conditioner and give your local HVAC company a call right away. Your technician will be able to inspect the problem and have your system properly thawed out.