Starite Heater Cycles on and off

[Rheinl271]

When I turn on the starite spa heater the temp shows 77 degrees. Outside air temp is 79.

I turn on the heater and have it set to heat to 104. The heater fires up normally, and runs 2-3 minutes then shows 180 temp followed by r8, and the heater shuts down, and service heater lite comes on. Then within a second it starts back up again and repeats this cycle. Any suggestion on which part is causing the issue?

 

[SoCalGuy]

I'd start with the thermal regulator. We had a similar issue with ours. Apparently it's a common failure on these heaters. About $50. Good luck.