De Dietrich 97580453 Ionisationssonde L70

This De Dietrich ionisation probe (article 97580453, also listed as 336.946.069) is a flame‑proving component for gas‑fired burners. Parts of this type are installed directly in the flame zone, where they use the rectifying effect of the flame to generate a small DC current that the burner control reads as a confirmed flame signal. Without a correctly functioning ionisation probe, the burner control will lock out during the safety‑time proving phase. Ionisation probes are selected by electrode length and bend, insulator diameter, the mounting flange or thread, and the gap between the tip and the burner earth. The probe must be positioned so that it is fully immersed in the flame but not struck by the direct spark. Typical failure modes include erosion of the tip, hairline cracks in the ceramic insulator, carbon sooting that bridges the gap, and a gradual drift of the gap that lengthens ignition or causes intermittent flame loss. On pilot‑fired burners the ionisation probe often monitors the pilot flame, which in turn lights the main burner; a faulty probe can prevent the main gas valve from opening. When replacing an ionisation probe on a burner of this class, check that the replacement matches the original in overall shape and insulator diameter. Clean the burner earth connection and inspect the wiring for insulation damage. The probe is a consumable item that should be inspected during every annual service, especially on burners with high cycle counts or dusty combustion air.