I need some help diagnosing a problem, please.
We have a Tiger River (Hot Springs) spa, older model. It is not big, but does great for its size for us. We are having temp problems, though. One Day, I will go out to check things, and the temp will be at 101 deg (my wife likes it warm) just like the thermostat setting says. It will go that way for a week or two. Then suddenly, I will find it at 110 or above. I turn down the thermostat, let it cool, then turn it back up 'til I here it turn the heater on. It will be set at about 85 deg on the dial. It will be there for a couple of weeks, then I will find it at 85 deg (burr!!) and I turn it back up and start all over again.
So, I am asking for help to diagnose the problem without replacing everything 'til I find it. What steps can I take to isolate it? How can I check the temp sensor? How would I determine the circuit board voltages and switching?
Any help would be appreciated.