Moinmoin! The ultraheat is an ingenious accessory. However, I found a small disadvantage worthy of improvement: the ultraheat is thermostatically controlled over the internal temperature. The switching times from the shutdown due to warm enough and the reconnection are relatively long in moderate cold. The ventilation works independently of the ultraheat. Now it is the case that the air hoses are naturally laid through the coldest corners of the trailer. (outside walls at the bottom) During the heating breaks is unnecessarily distributed by the passing ventilation a lot of cold air in the car. After some pondering and the good basic idea of Mr. NoGolf I have configured the cable tree to be seen in the picture. A temperature switch, switching threshold 40/25 °C, and a switch to finish the “automatic” in case of an emergency, parallel to it. The whole thing is switched into the connection of the engine. Now it is so that I switch the fan on and on to the desired position. The heater heats first and at a housing temperature of 40 °C. The fan is switched off staticly. And now the temperature switch from 25 °C. And then the temperature switch is still cool!