E444
Lennox
Accessory Control Error (Dehumidifier / Ventilation)
Thermostat displays E444; furnace may not respond to dehumidification or ventilation commands.
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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
Miswired dehumidifier terminals, Faulty Lennox dehumidifier or ventilation controller, Shorted accessory wiring, Incorrect accessory configuration in thermostat
How to Fix / Troubleshooting
Safety: Turn off power to furnace and any connected accessories.
- 1. Inspect accessory wiring: Check DEHUM, HUM, or ventilation terminals on the Lennox control board and accessory device. Ensure correct polarity and tight connections.
- 2. Disconnect suspect accessory: Temporarily remove accessory wires from the furnace board and see if E444 clears after a power cycle.
- 3. Verify configuration: In the thermostat installer menu, disable unused accessories or correctly configure installed ones.
Persistent E444 may indicate a failed accessory control module that should be replaced by a technician.
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Repair Difficulty
Medium
3/5
Required Part
Lennox Dehumidifier Control
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