Aprilaire digital humidifier control displays E7 and humidifier runs erratically or not at all

Safety first: Turn off power to the furnace and shut off the humidifier water supply.

• Inspect water panel: Open the Aprilaire humidifier cover and remove the water panel (evaporative pad). Check for heavy mineral buildup, crumbling media, or algae.
• Clean or replace: Replace the Aprilaire water panel (evaporative pad) with the correct model (e.g., 10, 12, 35, 45, 56, etc., depending on unit). Do not attempt to chip off heavy scale; replacement is recommended.
• Clean distribution tray: Remove the top distribution tray and rinse out mineral deposits from the slots and holes so water can flow evenly.
• Reset service indicator: Follow the control’s instructions (often holding the reset or up/down buttons for several seconds) to clear the E7/service reminder.
• Restore operation: Turn water and power back on, then call for humidity and verify even water flow over the new panel.