We have what Marathon calls, The "Canadian Heat Pkg" our our our last and present coach. Our cruise airs work down into the teens. One of our four isn't working correctly, and it used to blow hot, now its cool. Haven't yet addressed it since we are comfortable at present. Canadian Heat option pkg gives you also extra underbelly heaters both Webasto fired and electric. We also able to heat the coach's motor with the Webasto by a separate switch on the side dash.