The problem is that the temps in the cage drop below 80
but the probe that controls when the UTH turns on (it has to hit 80 to turn the UTH on to heat until 83F then turns off and has to drop to 80 again to repeat the cycle)
So basicly temps drop below 80, all the wya down to like 78 - 79 and the UTH probe does not. so it will not turn on the UTH