Carrier
Accessory Not Recognized by Thermostat
Thermostat does not detect or control installed Carrier humidifier, dehumidifier, or ERV/HRV.
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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
Accessory not enabled in thermostat configuration, Miswired accessory terminals, Incompatible accessory model, Failed accessory control board
How to Fix / Troubleshooting
Safety first: Turn off power to HVAC and accessories before wiring work.
- Step 1 – Enable accessory: In the thermostat installer menu, enable the specific accessory (humidifier, dehumidifier, ventilator) and select the correct type.
- Step 2 – Verify wiring: Confirm that accessory control wires are connected to the correct HUM, DHUM, or VENT terminals at both thermostat and Carrier control board or accessory.
- Step 3 – Check accessory power: Ensure the accessory has its required power supply and any local switches are on.
- Step 4 – Test accessory manually: If possible, use the accessory's local controls or jumpers to verify it operates independently of the thermostat.
- When to call a pro: If wiring and configuration are correct but control still fails, a technician should test the accessory control board.
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Repair Difficulty
Medium
3/5
Required Part
Carrier Humidifier Control Module
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