De Dietrich 95362450 exterior sensor AF60 (MCA 15 - MCA 25)

This article is the De Dietrich 95362450 exterior sensor AF60, also referenced as catalogue article 336.220.001. It is listed in the sensor components category and is identified for use with MCA 15 and MCA 25 units. The sensor is an outdoor temperature probe, a type of NTC (negative temperature coefficient) thermistor that reports the ambient temperature to the control board. Parts of this type close the control loop for weather compensation: the boiler modulates its output according to the outdoor temperature, so that flow temperature is reduced in milder weather and increased when it is cold. The sensor sits outside the building, typically on a north-facing wall, and is wired back to the boiler or system controller. On some installations the same type of sensor also provides a signal for frost protection functions. When selecting a replacement, the key parameters are the resistance characteristic (e.g. 10 kΩ or 12 kΩ at 25 °C), the cable length and the connector type. For outdoor sensors the cable must be weatherproof and long enough to reach the control board without a joint. Common failures are a drifting characteristic that makes the boiler modulate incorrectly, a broken cable, or moisture ingress. Always check the resistance at known temperatures and compare to the boiler manufacturer’s curve before fitting. The sensor is not polarity-sensitive.