E1
Viessmann
High-Pressure Protection / Refrigerant Circuit Overpressure
Indoor unit stops; E1 error displayed; may occur shortly after compressor start
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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
Blocked outdoor coil, Failed outdoor fan motor, Overcharged refrigerant, Non-condensable gases in system
How to Fix / Troubleshooting
Safety: High-pressure refrigerant is dangerous. Do not open the refrigerant circuit unless you are certified.
- Clean outdoor coil: Turn off power. Remove debris, leaves, and dirt from the outdoor heat exchanger fins using a soft brush and low-pressure water.
- Check outdoor fan: Restore power and observe the outdoor fan. If it does not start or runs slowly, the fan motor or capacitor may be faulty and should be replaced.
- Ensure clearance: Maintain at least the manufacturer-recommended clearance around the outdoor unit for proper airflow.
- Technician checks: If E1 persists, a technician should measure system pressures, verify refrigerant charge, and remove any non-condensables.
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Repair Difficulty
Professional Required
5/5
Required Part
Outdoor Fan Motor
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