If I hadn’t had to work on VWs and airplanes... I would never have suspected that they would design heaters that relied on exhaust gasses to heat their cabins. Seems and often is dangerous. I have some stories but will not bore people with them at this time.
“Seems dangerous” — no kidding. There probably isn’t much difference in pressure on the two sides of the heat exchanger, so exhaust gases could easily flow to the air side. I’m surprised we didn’t hear about more people succumbing to CO in the VW cabins.