E10
Ariston Defrost Sensor / Defrost Protection Error

Unit displays E10 and stops; often occurs during heating mode on heat pump models.

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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

Faulty outdoor coil defrost sensor, Sensor not detecting frost correctly, Defective defrost control on outdoor PCB, Excessive ice buildup due to low airflow

How to Fix / Troubleshooting

Safety first: Turn off power before working on the outdoor unit. Surfaces may be icy and slippery.

  • Step 1 – Inspect outdoor coil for ice: Check if the outdoor coil is heavily iced over. If so, leave the unit off to allow natural defrosting, or use warm (not hot) water to melt ice. Do not chip ice with sharp tools.
  • Step 2 – Check outdoor fan operation: Ensure the outdoor fan runs properly in heating mode. Poor airflow can cause excessive icing.
  • Step 3 – Inspect defrost sensor: Locate the defrost sensor (NTC) on the outdoor coil. Ensure it is firmly attached and wiring is intact.
  • Step 4 – Clean coil: After defrosting, clean the coil fins to improve heat exchange.
  • Technician tasks: If E10 persists, a technician should test the defrost sensor resistance, verify defrost cycle operation, and replace the sensor or outdoor PCB as needed.
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Repair Difficulty

Hard 4/5

Required Part

Outdoor Defrost Sensor (NTC)
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