Display shows DHW sensor error, water temperature unstable or unit shuts down

Safety first: Isolate power before accessing internal components.

Step-by-step checks:

• Power cycle: Turn the unit off for 30 seconds and back on to see if the error clears temporarily.
• Locate DHW sensor: On storage models, the DHW NTC is usually inserted into a dry pocket on the cylinder. On instantaneous models, it is clipped to the outlet pipe or integrated into the plate heat exchanger.
• Check connections: Ensure the sensor plug is fully seated on the control board and at the sensor. Look for damaged or pinched wires.
• Visual inspection: If the sensor is removable, check for signs of moisture ingress or corrosion. Clean the sensor pocket if scaled.

When to call a professional: If the sensor tests open/short with a multimeter or the error persists after reseating connections, have the DHW NTC sensor replaced by a technician.