Aprilaire bypass humidifier does not produce any moisture even though furnace is running

Safety first: Turn off furnace power and close the water supply before disassembling any water components.

• Check water supply valve: Locate the saddle or ball valve feeding the humidifier. Ensure it is fully open. For saddle valves, back the needle out completely.
• Test solenoid operation: Call for humidity and listen for a click at the solenoid. If no click, test for 24 VAC at the solenoid terminals. If voltage is present but no water flows, the solenoid is likely stuck or failed.
• Clean inlet screen: Shut off water, disconnect the inlet side of the solenoid, and remove the small screen filter. Rinse out debris and reinstall.
• Inspect tubing: Check the plastic or copper tubing from the solenoid to the water distribution tray for kinks, mineral blockage, or cracks. Replace if restricted.
• Replace solenoid: If the coil is open or the valve is stuck closed, replace the Aprilaire solenoid valve assembly and test for proper water flow over the water panel.