There are multiple reasons why your AC may be blowing boiling air. The thermostat is a wonderful place to start looking for the culprit. It sounds too simple. This is a usual reason why your air conditioner might be doing the opposite of what it should, but low refrigerant can cause your air conditioner to only blow boiling air, then do not attempt to service this yourself. Coolants, also known as refrigerants, can be easily dangerous. To purchase and handle this substance, you must be a licensed Heating, Ventilation and A/C specialist. Your Heating, Ventilation and A/C system’s air filters may seem unimportant, but they are essential. Heating, Ventilation and A/C filters disconnect dust, dander, and other airborne contaminants from the air reentering your apartment from the system, but 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 moderate 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, and frozen evaporator coils can cause your system to blow boiling air as well. Some things which can be preventing airflow to the evaporator coil include obstructed HVAC ducts, a dirty coil, or low refrigerant. If you find your system frozen over, turn off your air conditioner and deliver your local Heating, Ventilation and A/C supplier a call right away. Your specialist will be able to inspect the problem and have your system properly thawed out.