Carrier Humidifier Stuck On

Whole-home Carrier humidifier runs even when there is no call for heat or humidity.

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.

Possible Causes

Stuck humidifier relay on furnace control board, Shorted humidistat wiring, Miswired HUM terminals, Failed humidifier control

Safety first: Turn off power to the HVAC system before working on wiring.

Steps:

1. Check humidistat setting: Ensure the humidistat or thermostat is not set to a continuous or test mode.
2. Inspect wiring: Look for shorts between humidifier control wires, especially where they pass through metal knockouts.
3. Test relay: If the humidifier runs with the humidistat disconnected, the furnace HUM relay or control board is likely stuck closed and may need replacement.

Hard 4/5

Furnace Control Board (HUM Relay)

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