De Dietrich 100010843 temperature sensor AD240

De Dietrich temperature sensor AD240, catalogue article 336.220.006, also listed under manufacturer code 100010843. This part falls under the category of temperature NTC sensors. NTC sensors of this type are used to measure water or air temperatures in a boiler system – typically flow, return, cylinder or outdoor temperature – and send the signal to the boiler control board. This closes the control loop, allowing the burner to modulate its output correctly in response to heat demand. When selecting a replacement for a part of this type, the key parameters are the resistance characteristic (for example 10 kΩ or 12 kΩ at 25 °C), the probe form (immersion, clamp-on or sleeve), cable length and connector type. For mechanical thermostats and limit switches (which act directly rather than through the board), switching point and reset type also matter. Common failures for such sensors include a drifting resistance characteristic that makes the boiler modulate wrongly, a broken cable, or poor contact between a clamp-on probe and the pipe. Ensure the replacement matches the original sensor’s resistance curve and physical mounting arrangement.