I just bought a Legacy Whirlpool Spa made by Master Spas. It has a Balboa M7 system. The Spa is about 3-5 years old and not used for the past 5-6 months. Got it installed and everything was running fine, jets, pump, light etc... Temp started at 53 degrees and got up to 63. I went to check on it before going to bed and it was shutdown. No pump, no jets and no light. The display had error code "HH". Manual says it's in an overheat situation but what was still cold. The next day I did some troubleshooting. The error code then went to "SB" which is a problem with sensor B. Swapped wires and error said "SA"(sensor A). This is my 1st hot tub so I'm no expert but this tells me I have a faulty sensor B. Several forums said when a sensor is changed to change both sensors. I have ordered 2 more sensors and hope this is the correct resolution.

The temperature sensors do not seem very complicated. Looks like a small metal rod with a wire attached to it. My question is, how can this part go bad? Is it more complicated than it looks?