I don't think there is a real good place for case sensor. If you put it anywhere near a fan blowing in then it will read wrong, might work closer to a fan sucking air out of the case. No idea, didn't see any good place to put one.
Try hanging it into the center of the case, top, front, back and see.
<font color=red>We born naked and screaming, then it gets worse.</font color=red>