Honeywell 139278 Auxiliary Micro Limit Switch

The Honeywell 139278 is an auxiliary micro limit switch designed for precise control in industrial and HVAC applications. This SPDT (Single Pole Double Throw) switch provides reliable switching for low to medium current loads, rated at 10A at 120V AC and 5A at 240V AC. It features a compact, durable phenolic housing with screw terminals for easy wiring and a plunger actuator for mechanical activation. Commonly used in gas valves, appliances, and automation systems to detect position limits or provide interlock functions, it offers high repeatability and long mechanical life, often exceeding 10 million cycles. Advantages include its robust construction resistant to vibration and shock, making it superior to generic switches in harsh environments. Drawbacks may include limited suitability for high-current or DC applications without derating. Based on attached images, the unit appears used with minor wear on the actuator and housing, but terminals are intact; faceplate shows part number 139278 and possible serial/markings like B124. No parent/child assets visible. Estimated market price for used condition: $15-30 USD. For datasheets, refer to Honeywell's official site (e.g., search 'Honeywell micro switches catalog PDF' at sensing.honeywell.com).