E23
A.O. Smith Evaporator Coil / Refrigerant System Fault

A.O. Smith hybrid heat pump water heater shows E23 and may revert to electric-only mode

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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, Blocked evaporator coil, Failed temperature or pressure sensor in heat pump circuit, Heat pump compressor fault

How to Fix / Troubleshooting

Safety: Turn off power. Do not attempt to open the sealed refrigeration system yourself.

  • 1. Clean air filter: Remove and clean or replace the air filter on the heat pump intake. A clogged filter can cause coil freeze and faults.
  • 2. Inspect evaporator coil: Check the coil for dust buildup. Gently vacuum or brush the fins without bending them.
  • 3. Check airflow: Ensure there is adequate clearance around the unit for air circulation per A.O. Smith guidelines.
  • 4. Mode selection: Switch the unit to standard electric mode to maintain hot water while awaiting service.
  • 5. Professional service: A licensed HVAC technician must check refrigerant charge, compressor operation, and heat pump sensors.
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Repair Difficulty

Professional Required 5/5

Required Part

Heat Pump Compressor and Evaporator Coil
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