Truck mounted heat exchange device

A device for heating a fluid for use in carpet cleaning is provided. Specifically, the device routes a source of exhaust toward and/or around a heat exchange chamber to heat a fluid in a controlled manner. The fluid may be heated to a maximum amount when the full amount of exhaust is flowed through the heat exchange chamber. The fluid may not be substantially heated when the exhaust is flowed around the heat exchange chamber through an exhaust bypass. The fluid can also be heated to an intermediate amount by flowing some, but not all of the exhaust through the heat exchange chamber and the rest of the exhaust through the bypass.