ActronAir Coil Sensor 3-Pin JST is an NTC temperature sensor for ActronAir residential split ducted systems, monitoring coil temperature via a 3-pin JST connector for coil protection, defrost management, and capacity control functions on the system PCB. Confirm the cable length and thermistor specification against the system service documentation before ordering -- multiple coil sensors with 3-pin JST connectors exist across different system generations with different thermistor ratings. Isolate power at mains before replacing any coil temperature sensors.