Boiler displays E05, no heating or hot water, flow temperature sensor fault indicated.

Safety first: Isolate electrical power before opening the boiler casing.

• Locate the flow sensor: On Weishaupt boilers, the flow NTC is usually clipped or screwed into the flow pipe leaving the heat exchanger, connected by two small wires to the control board.
• Check wiring and connector: Inspect the plug and wiring for signs of corrosion, overheating, or mechanical damage. Reseat the connector firmly.
• Measure sensor resistance: With the boiler off and the sensor disconnected, measure resistance with a multimeter. Compare the reading to the temperature/resistance table in the Weishaupt manual (e.g. around 10 kΩ at 25 °C, model dependent). If the reading is open, shorted, or far out of range, replace the sensor.
• Reset and test: After replacing or reconnecting, restore power, clear the fault (if required), and run the boiler to confirm normal operation.

When to call a professional: If the sensor tests correctly but the control still reports E05, the control board may be faulty and should be diagnosed by a technician.