A10
Sime
DHW Temperature Sensor Fault
Furnace indicates a domestic hot water (DHW) sensor error on combi models; hot water may be unstable or unavailable.
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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 NTC sensor, Loose sensor connection, Scale buildup around sensor pocket, Faulty control board input
How to Fix / Troubleshooting
Safety first: Turn off power and close water isolation valves before removing any water sensors.
- Access DHW sensor: On Sime combi furnaces, the DHW NTC is usually mounted on the plate heat exchanger or DHW outlet pipe.
- Inspect wiring: Check the sensor connector and cable for damage. Reseat the plug on the control board.
- Test sensor: With power off, disconnect the sensor and measure resistance. Compare to Sime specifications for the current water temperature. Replace if out of range.
- Descale if necessary: Heavy scale around the sensor pocket can cause incorrect readings. A technician can descale or replace the plate heat exchanger if needed.
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Repair Difficulty
Medium
3/5
Required Part
DHW NTC Temperature Sensor
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