I have a balboa SUV m-7 spa package. About a year agao, my heater failed and I replaced it with a new heater from balboa. Recently, the heater stopped working again. The spa would start up normally, and I was able to set a desired temp. The heat light would come on, but the spa was not getting hot. I took it apart and checked to see if the heating element inside the tube was corroded. It was not. That led me to believe that it could be as simple as one of the temperature probes being bad. Since I had the two from the previous heater, I tried swapping them out in different combinations, hoping that 2 of the 4 were still good.

Is it possible that the probes are bad? If so, is there any test that can be done to identify the good ones?

Is there a way to test the heating element itself?

If the probes don't normally go bad, what would be the next thing to test?

Also, after trying the last combination of probes and turning the spa back on, the temp display now just cycles through the possible temps from 80-104 and then back down over and over.

Have I potentially caused/uncovered a new problem?

The spa is about 4 years old, so out of warranty.

Any help is greatly appreciated.