Aprilaire Humidifier works when furnace on only

[Bler57]

I have the Aprilaire 600 with the Model 60 automatic controller. The humidifier works as advertised when the furnace is on but in the blower mode the fan runs and the humidifier on light is illuminated but the solenoid doesn’t open. I have checked continuity on the temp sensor and it is good. All wiring is correct. What could be the issue. It’s like the humidifier circuit is only receiving power when the furnace is activated. Furnace is an American Standard Freedom 80 Single Stage. About 12 years old.

Thanks, Kurt

 

[AC Power]

Your request is dated March 29th. Nobody has answered this yet?

The solenoid may not open if a humidistat has reached it's target setpoint. I am assuming you have a humidistat on the wall in your main living area...usually near the thermostat?