Rear window defogger and heated mirrors not working

Re: Rear Window Defrost & Front Mirrors Defrost Folks, an important option is available on our X. If you find that all of the windows are fogging up in colder mos, you may have AUTO DEFOG turned OFF. This is a feature that cycles the A/C on a bit to de-humidify air in the cabin when and heat is used. It is very different than the electric grids used on rear window and side mirrors to melt ice/defog them. The Auto Defog feature can be turned On or OFF in Config menu, under CLIMATE & AIR QUALITY sub menu, right from the dash. I turn mine OFF in the Summer as it causes the A/C to blow a bit cooler than I want, when it senses cabin humidity building, not always when I want less chilly air blowing on me. But now in Winter, moisture fogs our windows often so, I just turned mine ON again, recently. The REAR defog button will not help us clear side windows sufficiently,at times, when only your heater is blowing, with this feature deactivated................ here is my original post: Re: Too much Air conditioning? Think I got it! This sled has an "Auto defog" feature that senses humidity build-up and turns on the A/C to condense the moisture in the cabin air.(if the air/vents/defrost are already ON ) It will turn the A/C ON without showing it on the display lights! This will result in the air feeling colder than it did a minute or 2 ago when air vents were first turned ON. A few minutes later it may turn the A/C OFF, also w/o notice To eliminate the phenomenon, press Config to get to Vehicle Personalization menu, from the center stack, and dial into Climate & Air Quality options. Turn OFF the Auto Defog - HTH Rob

Still don't work but thanks for your help. The car is going back to the dealer to have the radio replaced (another known issue) and they will look into this again. There seems to be a known problem with rear defoggers and GM vehicles. Just trying to find out an answer.