The fan does not seem to be running. How can I determine what the problem is? I'm not sure if it's the fan, solenoid or the computer board.
humidifiers can be complex devices. first step is check power at the board and make sure you haven't blown a board fuse or a fusible link. assuming the board has power, check to see if the fan gets power when you turn on the power. if no power to the fan, and all the wires are good, then chances are the power supply on the board is shot, or the control module is shot. does it have momentary switches or good old fashioned "click" knobs or switches )ie SPST or DPST?