My 04 and 05 have a button simply labeled 'REAR'. My understanding of the system is that this is a defeat switch if someone in the back leaves it on as you cannot control temp or fan speed, just simply on or off. From the back controls you can turn it on and off or adjust the temp. For instance, if you set the front controls for 'COLD' and someone in the back says they're hot and want AC, if you just hit the 'REAR' button up front, all it will do is turn on the rear system. If it's set at 90, the rear passengers are going to get heat. It's up to them to set the temp.