Abstract: An example humidifier controller for operation in conjunction with an air conditioning/furnace unit is presented. The humidifier controller may include a control circuit to generate a fan control output for the air conditioning/furnace unit. The fan control output may be equal to a fan control input in response to any of a heating control signal, an air conditioning control signal, and the fan control input being active. Also, the fan control output may be based on a humidistat output in response to each of the heating control signal, the air conditioning control signal, and the fan control input being inactive.