Atlantic Diverter Valve / Hydraulic Selector Fault

Boiler works for heating but not for domestic hot water (or vice versa), with no error code displayed.

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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

Stuck diverter valve, Failed diverter motor, Blocked DHW or heating circuit, Faulty position sensor

How to Fix / Troubleshooting

Safety: Allow the system to cool before touching pipework.

  • Test both modes: Call for heating only, then DHW only, and observe whether the boiler responds correctly.
  • Feel pipes: On DHW demand, the DHW outlet should get hot; on heating demand, the flow to radiators should get hot. If not, the diverter may be stuck.
  • Exercise the valve: Repeatedly switch between heating and DHW demands to see if the valve frees up temporarily.
  • Professional repair: A technician should clean or replace the diverter valve assembly or motor and flush any blocked circuits.
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Repair Difficulty

Hard 4/5

Required Part

Diverter Valve Assembly
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