F0
Challenge General Sensor Fault / Sensor Circuit Open

Humidifier or dehumidifier shows F0 and stops operating.

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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

Any of the NTC sensors (ambient, evaporator, defrost) disconnected, broken sensor harness, sensor connector not seated on PCB

How to Fix / Troubleshooting

Safety: Unplug the appliance before opening the cabinet.

Steps:

  • Identify sensors: Most Challenge units have at least an ambient temperature sensor and an evaporator sensor. Locate each sensor and follow its wires to the PCB.
  • Check all connectors: One by one, unplug and firmly replug each sensor connector on the main PCB.
  • Inspect harnesses: Look for pinched, cut, or chewed wires, especially where they pass through metal brackets.
  • Test sensors: If you have a multimeter, measure resistance of each sensor at room temperature. Replace any that read open circuit or short.
  • Replace defective sensor: Install the appropriate Challenge NTC sensor (ambient, evaporator, or defrost) matching the failed component.

Note: If all sensors test good and F0 persists, the main PCB sensor input may be faulty.

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Repair Difficulty

Medium 3/5

Required Part

Ambient or Evaporator Temperature Sensor (NTC)
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