F23 error, appliance stops, temperature difference between flow and return is excessive

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

Blocked heat exchanger, Pump not circulating (on system models), Closed valves, Air lock in circuit

Safety first: Isolate power and allow the system to cool.

Check valves: Ensure all isolation valves on the primary circuit are open.
Verify pump operation: On models with an internal pump, listen or feel for pump operation. If silent or very hot, the pump may be seized.
Bleed system: Remove air from the primary circuit using bleed valves and automatic air vents.
Descale or flush: If blockage is suspected, flush the system and/or descale the heat exchanger.

Warning: Running with poor circulation can cause rapid overheating and component failure.

Hard 4/5

Primary Circulation Pump

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