Davey Spa-Quip in line Heater Temp Sensor. Fits SP400, 54500, 500A, 500AMK2, SP600, SP601, SP800, SP1200. May be the cause of Error 8 / Error 08 / ER 08. Note that in some cases when a thermistor has failed or is giving false readings, there is underlying corrosion, and it may be best to replace the entire heater assembly.
These are held in by glued heat shrink which will need to be replaced. Originally had a dipped yellow end, but now has a red over-moulded end.
Temperature Sensor Suits: Spa Power 400, 54500, 54500A, 500A MK2, Spa Power 500, Spa Power 600, Spa Power 800 , Spa Power 1200