Ariston hybrid/heat-pump water heater shows E20; heat pump mode disabled, unit may run only on electric backup.

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.

Possible Causes

Compressor overload or failure, Low refrigerant charge, Blocked evaporator coil, Faulty compressor start capacitor or relay

How to Fix / Troubleshooting

Safety first: Disconnect power. Refrigerant systems must be serviced by certified HVAC technicians.

Check airflow: Ensure that the evaporator air intake and discharge are not blocked. Clean filters and coils with a soft brush or vacuum.
Listen for compressor: When powered, note if the compressor attempts to start or just hums and trips. Do not repeatedly force starts.

Do not attempt to open the sealed refrigerant circuit. Contact an authorized Ariston service center to check refrigerant charge, compressor health, and associated components.

Repair Difficulty

Professional Required 5/5

Required Part

Compressor Assembly

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