E5
Aprilaire
Humidifier Output Circuit Fault
Aprilaire digital humidifier control displays E5 and humidifier will not energize the solenoid valve
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Shorted solenoid valve coil, Shorted H terminals wiring, Burned output relay on control, Incorrectly wired to 120 V instead of 24 V
How to Fix / Troubleshooting
Safety first: Turn off power to the furnace and shut off water supply to the humidifier before testing.
- Inspect solenoid wiring: Locate the Aprilaire solenoid valve on the water line. Check the two low-voltage wires from the control H terminals to the solenoid. Look for pinched, cut, or melted insulation.
- Test solenoid coil: Disconnect one solenoid wire and measure resistance across the coil. Typical Aprilaire 24 VAC solenoids measure 20–60 Ω. A reading near 0 Ω indicates a shorted coil; OL indicates open.
- Check for shorts: Verify the H wires are not connected to any 120 V source. They must only be on the 24 VAC control circuit.
- Replace failed parts: If the solenoid is shorted, replace the Aprilaire solenoid valve assembly. If wiring and solenoid test good but E5 remains, the control’s output relay is likely damaged and the Aprilaire digital humidifier control should be replaced.
- Retest: Restore power and water, then call for humidity and confirm the solenoid energizes without errors.
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Repair Difficulty
Hard
4/5
Required Part
Aprilaire Solenoid Valve
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