Rodger, I leave my block heater on all the time this time of year. How do you keep the coach from freezing if you only run the Webasto every now and then? I run a couple of CruiseAirs set on 60 degrees unless the temp is going below freezing. If freezing temps are forecast, I turn the Webasto on and set it at 55 to 60. I'd sure rather burn a little diesel than fool with any frozen water lines. CruiseAirs are useless when the outside temp is below something around 45 degrees.