Abstract: A truck has a cab, a body, an engine, and an exhaust system. The body carries loads during use and each of its panels has an interior fluidly connected to one another. The exhaust system receives exhaust from the engine which flows thru exhaust pipes into a muffler and then into a diverter box. When desired, the diverter box diverts at least a portion of the exhaust air into an air outlet that directs air to the interiors of the panels to heat the body during use. Any remaining portion of the exhaust air, is exhausted directly to ambient air. A circuit controls the flow of exhaust gases to the truck body utilizing a diverter, an actuator for controlling the diverter, and a temperature sensor for controlling the actuator wherein a flow of exhaust gases to the truck body is shut off when said temperature sensor senses an exhaust gas temperature above a predetermined level. Alternatively, a signal indicating the start of a regeneration cycle of a diesel particulate filter can be used to control the actuator.