Temperature sensor for Balboa M7 heaters. The M7 system uses two identical probes placed at either end of the heater. The probes have two-pin plugs which connect to sockets on the motherboard of the hot tub control system.
Two versions of this sensor are used in control systems with integrated heaters: the 30 cm version (shown in the photo) is generally found in control systems housed in plastic boxes, while the 60 cm version is more commonly found in metal-boxed systems.
A third version, with a 90 cm cable, is used in systems where the heater is separate from the control box.
Sensor diameter: 6.3 mm (1/4″)
Plug: a 2-pin connector with a black wire and a red wire