E2
Aprilaire
Indoor Temperature Sensor Fault
Aprilaire digital humidifier control shows E2 and humidifier does not operate automatically
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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
Failed internal temperature sensor in control, Control exposed to extreme temperatures, Control circuit board damage, Incorrect mounting causing overheating or condensation inside control
How to Fix / Troubleshooting
Safety first: Turn off HVAC power before removing or rewiring the Aprilaire control.
- Check mounting location: Ensure the digital humidifier control is mounted on an interior wall or return duct per Aprilaire instructions, away from heat sources, direct sunlight, or supply air that could damage the internal sensor.
- Inspect for moisture: Remove the control cover and look for signs of condensation, corrosion, or water damage on the circuit board. If present, correct the moisture source (duct leakage, poor mounting) and allow the control to dry completely.
- Power cycle: Turn power off for 2–3 minutes, then restore power to see if the E2 clears. Transient faults sometimes reset.
- Check wiring: Verify all low-voltage connections (R, C, W, H, ODT, etc.) are tight and not shorted. Shorts can damage the internal sensor circuitry.
- Replace control: If E2 persists and wiring/location are correct, the internal temperature sensor is likely failed. Replace the Aprilaire digital humidifier control with the same model and reconfigure per the installation manual.
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Repair Difficulty
Medium
3/5
Required Part
Aprilaire Digital Humidifier Control
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