Can anyone tell me a bit more how the freeze control works on a SP2603VSP? Does it have a probe that measures air temprature? I left it at the default setting which I beleive was 37 degrees. It is kicking on when the temperature is in the 40s, which isn't too bad. However, it is still running when it is 59 degrees outside. Is there a way to see what temperature it think it is? Is it measuring water temperature?