Viessmann
Loss of Cooling Capacity
Indoor unit runs but no cooling; air temperature hardly changes
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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
Low refrigerant charge due to leak, Severely dirty indoor or outdoor coils, Indoor fan running too slowly, Expansion valve malfunction
How to Fix / Troubleshooting
Safety: Turn off power before cleaning. Refrigerant work must be done by a certified technician.
- Clean filters and coils: Wash indoor filters and clean both indoor and outdoor coils with appropriate coil cleaner.
- Check fan speeds: Ensure indoor fan responds to speed changes and airflow is strong.
- Check mode and setpoint: Confirm the unit is in cooling mode with a set temperature at least 3–5°C below room temperature.
- Technician diagnosis: If performance remains poor, a technician should check refrigerant charge and expansion valve operation.
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Repair Difficulty
Hard
4/5
Required Part
Electronic Expansion Valve
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