On my model 600 Aprilaire humidifier the solenoid does not operate on my humidifier, even when in test mode. I am having the same problem. I have put the wires directly on the 24V terminals and solenoid does open. There are no error codes or flashing lights and everything else is wired and working properly. How do I focus on the humidistat itself? Where should I start? This is a brand new unit which has never been used before.
Thank you for contacting us with regards to your Model 600 Humidifier. We would recommend focusing on the humidistat and its wiring. We have two digital humidifier controls, and there weren’t any indicators as to which one you had. Both of them are looking for continuous 24v to power them and an intermittent 24v to tell them when your furnace is active. It is designed to wait for a signal from the furnace to turn on the humidifier. We would recommend contacting your installer and have them double-check the wiring.