A drain pan level monitoring system of an air conditioning system comprises a level sensor that generates a level sensor output signal related to a sensed level of condensation buildup within a drain pan. A method of monitoring a liquid level buildup in a drain pan of an air handling unit comprises determining a level of liquid buildup in the drain pan and determining whether an action should be taken in response to the determined level of liquid buildup by comparing the determined level of liquid buildup to a predetermined value. A method of preventing liquid overflow of a drain pan of an air handling unit comprises monitoring a pressure related to a liquid level buildup within the drain pan and taking an action when the pressure meets a predetermined criteria.