Honeywell Home
Accessory Control Configuration or Wiring Fault
Thermostat cannot control humidifier or dehumidifier as expected
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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
Humidifier/dehumidifier not wired to correct terminals, Accessory not enabled in installer setup, Incorrect control type (powered vs dry contact), Failed accessory relay
How to Fix / Troubleshooting
Safety: Turn off power to HVAC and accessory equipment before working on wiring.
- Verify accessory wiring: Confirm that the humidifier or dehumidifier is wired to the correct accessory terminals on the Honeywell Home thermostat or equipment control board.
- Enable in installer setup: In the thermostat’s advanced settings, enable humidification/dehumidification control and select the correct type (e.g., powered, fan interlock).
- Test accessory manually: Temporarily jumper the accessory control terminals at the equipment to verify the humidifier/dehumidifier itself operates.
- Replace relay or thermostat: If the accessory works when jumpered but not via the thermostat, the accessory relay or thermostat output may be faulty and require replacement.
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Repair Difficulty
Hard
4/5
Required Part
Humidifier/Dehumidifier Control Relay
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