Furnace display shows domestic hot water (DHW) sensor error; unstable or no hot water on combi models
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.
Possible Causes
How to Fix / Troubleshooting
Safety: Turn off power and close water valves if opening any water-side components.
- Locate DHW sensor: On IVT combi or indirect systems, find the DHW sensor on the hot water cylinder pocket or attached to the plate heat exchanger.
- Check seating: Ensure the sensor is fully inserted into the pocket and secured with its clip or clamp. Apply thermal paste if specified by IVT.
- Inspect wiring: Trace the sensor cable to the control board. Reseat the connector and check for damage.
- Test sensor: Measure resistance and compare to the IVT chart. Replace the sensor if readings are out of range.
Persistent DHW temperature issues after sensor replacement may indicate scaling in the heat exchanger or control board faults, requiring professional service.
Repair Difficulty
Required Part
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