Originally Posted by aswallie
Oh, I can help with this one! To those saying pull the defrost and put a diesel heater in BussyMcBusface did this and ended up cracking their windshield. It's a fine line you need to walk by having enough heat but not too much.
As far as pulling heaters and keeping the defrost working we ran new lines down the middle of the bus from our engine to the front. Sorry for the Instagram link but it's the easiest way to show you.
Well, just because one guy did it the wrong way, doesn’t mean it cannot be done a right way. The air hitting my windshield is warm, but no hotter than the standard defrost air in any of my other vehicles. I can hold my hand at the defrost vent when it is running at 100%. I can also mix it with fresh air or redirect the heat to the cabin.
The problem is likely that BussyMcBusface had the exit air from the heater blowing directly onto the windshield. That could be around 200°F, more or less.