H2
Carrier
Humidifier Water Flow / Solenoid Fault
Carrier furnace/thermostat indicates H2 and bypass or fan-powered humidifier does not run.
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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 humidifier water solenoid valve, Clogged inlet screen on solenoid, No 24 VAC signal from furnace board, Broken wiring between furnace HUM terminals and solenoid
How to Fix / Troubleshooting
Safety first: Turn off furnace power and shut off the water supply to the humidifier before servicing. Water and electricity are both hazards.
Steps:
- 1. Check water supply: Ensure the saddle valve or shutoff feeding the humidifier is open and that the supply line is not kinked.
- 2. Inspect solenoid valve: Locate the Carrier humidifier solenoid on the water line. Remove the inlet screen (if accessible) and clean any debris.
- 3. Verify 24 VAC signal: With furnace calling for heat and humidifier enabled, measure voltage at the solenoid coil terminals. You should see ~24 VAC. If not, check wiring back to the furnace HUM and C terminals or humidifier control.
- 4. Test solenoid coil: With power off, measure coil resistance. An open coil indicates a failed solenoid that must be replaced.
- 5. Replace solenoid: Install the correct Carrier humidifier solenoid valve, using new compression fittings or ferrules as needed. Check for leaks after restoring water.
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Repair Difficulty
Hard
4/5
Required Part
Humidifier Water Solenoid Valve
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