FAG furnace with Honeywell H49A humidistat and Aprilaire 220-224 humidifier. Solenoid controlling water flow to humidifier not responding to blower motor on/off. When blower motor is off, manually turning humidistat higher causes water to flow to humidifier; manually turning it down causes water to stop. Any hints as to why it is not operating according to blower motor on/off signal? It is my understanding that when the blower is off, manually adjusting the humidistat should not cause water to flow/stop. Manually adjusing humidistat should cause flow only when blower is on, correct? Thanks for the help!

Thanks for the reply. The humidifier was wired to the 24v transformer only, so it wasn't communicating to the furnace. I created a circuit from one post of the transformer to the furnace board R power terminal, and from the W heat terminal to the other post of the transformer. Now the humidifier water solenoid comes on and off during calls for heat.