Originally Posted by MetalMan2004
I have the fan set to come on at 75 and cut off at 70.
Is your probe measuring wort or ambient temperature?
70-75 degrees ambient (or wort for most yeast) in your chamber is too high.
Not that it makes any difference if the fan is not shutting off,
but if you have luck adding more bottles set the fan in the 64-68 range.
Your wort will be a good 5 degrees higher than ambient.