While designed for Robertshaw ignition controls

Thermal Resistance: Specifically engineered insulation prevents melting or grounding out when routed past hot furnace components

a reading of "OL" or open loop indicates a broken coil

you can use a longer lead as long as the excess copper tubing is carefully coiled away from the flame and high-heat zones

Standardized Fit: Black color-coded spring allows for rapid identification during field service and inventory management

Lochinvar & A.O. Smith 100278231 Coupler 30067439-890 While designed for Robertshaw ignitionThe Lochinvar & A. O. Smith 100278231 Coupler is a precision engineered pump coupler replacement designed for high performance hydronic and domestic hot water systems. As a critical mechanical link between the motor and the pump assembly, this genuine OEM part ensures smooth torque transmission while compensating for minor shaft misalignments that can lead to premature bearing failure. This specific model is the direct technical replacement for the