Moin, I finally managed to get a preheater. Have installed everything in the bay at a used Webasto Thermo Top T BW50 Bj.:2002. As far as everything is good, but now I ask myself where I should plant the in my moto room still quite installed there. I have read that the original heater under the driver’s headlight should sit behind the bumper or fender, that would be like me also the only free place, otherwise I don’t think so, you maybe? I have to put the hoses right across the engine room, so the enclosed ones will not be enough, therefore I have to get longer anyway. Achja, the whole should be in my Audi 100 C4 avant quattro with the 2.3l AAR and climate control. Because of the connection of the air conditioning I have already found a lot here and will probably implement this also, say automatic control with 22° and ventilation level 4. Now it’s all about the integration into the return of the benzoin line, just behind the volume divider, and this is something that I wanted to do there.