The Finder relay mod. 55.13, 24V AC coil, is a Series 55 industrial relay with 3 changeover contacts and a contact rating up to 10A, designed for PCB mounting. It works as an electromechanical switch: the coil, powered at 24V AC, pulls in the armature and simultaneously switches the three changeover contacts, allowing several circuits (e.g. heating elements, solenoid valves, auxiliary motors) to be driven from a single low-power control signal.

Replace it when the contacts are burnt or oxidised (the command no longer switches the load), when the coil is open-circuit (no click on energising), or when switching becomes intermittent or noisy, a typical symptom of contact wear after years of duty cycles.