A method for producing a structural element having a low density and high temperature resistance, where a plurality of hollow spheres made of a high temperature resistant material are connected together in a material fit, is disclosed. A side sensor is configured to detect an object, in a restraint dependent detection zone along a side of the vehicle, and generates an object detection signal. The present invention uses a polyester, such as one that includes unsaturated polyester, in combination with other resins, including an acrylic, crosslinking agent and conductive pigment to create a conductive primer that can be cured at low temperatures. In one embodiment, the heat exchanger is an air-to-air heat exchanger, and in another embodiment, the heat exchanger is an air-to-liquid heat exchanger.