A9
Worcester Bosch DHW Outlet Temperature Sensor Fault

Boiler displays A9, may have issues with hot water temperature regulation.

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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

Failed DHW outlet NTC, Poor thermal contact between sensor and pipe, Wiring fault to sensor

How to Fix / Troubleshooting

Safety first: Isolate electrical supply before removing covers.

Engineer steps:

  • Locate the DHW outlet NTC sensor on the hot water outlet pipe.
  • Ensure the sensor is firmly clipped and in good contact with the pipe.
  • Measure resistance and compare with NTC chart; replace if out of specification.
  • Inspect wiring harness for damage or loose connectors; repair as needed.
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Repair Difficulty

Medium 3/5

Required Part

DHW Outlet Temperature Sensor (NTC)
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