Vaillant Evaporator Icing / Low Airflow or Low Charge

Indoor unit coil freezes into a block of ice during cooling

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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

Very dirty filters or coil, Indoor fan running too slowly, Low refrigerant charge, Thermostat set too low with continuous operation

How to Fix / Troubleshooting

Safety: Turn off the unit and allow ice to melt before further operation.

  • Defrost: Leave the unit off with the front panel open until all ice has melted. Place towels to catch dripping water.
  • Clean filters and coil: Wash filters and clean the evaporator coil with a soft brush or coil cleaner.
  • Check fan speed: Run the unit and ensure the fan responds to speed changes. If airflow is weak, inspect the fan motor.
  • Moderate setpoint: Avoid setting the temperature extremely low; use 23–25°C for cooling.
  • If icing recurs: A Vaillant technician should check refrigerant charge and system pressures.
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Repair Difficulty

Medium 3/5

Required Part

Indoor Air Filter
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