High Limit thermistor 39530 fits Watkins Limelight, Tiger River and Hot Spring spas, made from 2002-2013. Includes threaded thermistor, 24"" cable and a 4-Pin connection plug. 5/8"" diameter bulb or threaded black thermistor screws into the hi limit inlet port, with an o-ring to make a seal. The other end of the cable plugs into your hi-limit port on the spa control. Mates with companion Hi-Limit 39525.
Spa heaters are usually controlled with the use of two (2) thermistors or high limits, and if you are replacing one, it is always thought best to replace the both thermistors together, so when one goes bad, replace them both is the conventional wisdom. Symptoms of a failing hi-limit thermistor in Hot Spring and Tiger River spas is your actual spa temperature lower than displayed temperature, or when Hot Springs topside panel ready light is steady blinking. Other systems may show an HL error fault code.