Honeywell Temperature sensor SO70004

This Honeywell temperature sensor is an NTC (Negative Temperature Coefficient) device. Its SKU is SO70004, equivalent to Honeywell T7335C2008, and it supersedes part numbers 70190121 and 87381013120. It is used in Dakon DUA, Dakon Dua, and Dakon Kompakt boilers. The sensor reports temperature readings to the control board, providing input used for burner output modulation and three-way valve positioning.

When selecting a replacement NTC sensor of this type, key parameters are the resistance characteristic (for example 10 or 12 kOhm at 25 °C), probe form (immersion, clamp-on, or sleeve), cable length, and connector type. The exact values must be verified against the original specification or the control board manual before ordering. Ensure the new sensor matches the resistance curve of the original and is installed at the correct position, with the same immersion depth or pipe contact area, to avoid false readings.

Common failure modes for NTC sensors include a drifting resistance characteristic, which causes the boiler to modulate incorrectly, a broken cable, or poor thermal contact between a clamp-on probe and the pipe. These issues typically result in incorrect temperature readings or erratic burner behavior.