2006 Dodge Ram 1500 Pickup Owner's Manual - Page 284

284 UNDERSTANDING YOUR INSTRUMENT PANEL Circulation The cab is designed with features to promote outside air circulation. There are grilles in the cab back panel. These are air exhausters that provide the means for regular exchange of cab air. Side window demisters direct air flow specifically to the window glass to help prevent interior fogging of the glass. They are located in the extreme outside upper edges of the instrument panel. The demisters also provide extra air ducts for circulation. They are in operation whenever the Floor, Mix or Defrost modes are in use. NOTE: When you turn off the engine you may hear a hissing sound from under the hood for a short period of time. This is a normal condition that occurs if the air conditioning system has been on. It is not an indication of a problem with the air conditioning system. Rear Air Duct-Mega Cab Only Mega Cab Rear Air Duct The rear seat will receive air flow in all modes except for Defrost. The rear air duct is designed to be pointed up when in A/C mode, and pointed down in Heat mode.