Hot Spring Spas 1995 - 2002 Temp(Control) SensorHot Spring and Tiger River Spas 1995 2002 Temp(Control) sensor. These sensors are commonly used in controllers pre 2002 and are plugged into the side of the box, if your sensor is plugged into the main PCB inside the IQ2020 box then you will require the following HS 39205. Sensor has a cable length of 970mm and a thread width of 16mm(Larger then the Hi Limit sensor). It is recommended to also replace the Hi Limit sensor at the same time if replacing