Safety: Unplug the unit and allow it to cool before opening. Heating circuits involve mains voltage and high temperatures.

Steps:

Confirm mode: Ensure the warm mist or preheating mode is actually selected on the control panel.
Check for warm-up time: Some models require several minutes to heat. Wait 5–10 minutes and check again.
Access heater assembly: Open the housing to locate the preheating element and its wiring.
Inspect wiring and connectors: Ensure all heater wires and connectors are secure and not burned.
Test continuity: With the unit unplugged, test the heater element and thermal fuse for continuity using a multimeter. An open reading indicates a failed component.
Replace failed parts: Replace the preheating element or thermal fuse with original-spec parts. Ensure proper insulation and routing of wires.
If heater tests good: The main control PCB may not be energizing the heater relay and may need replacement.

Humidifier mist is cold when warm mist is expected (on models with preheating)

Possible Causes