I have the same problem but on the passenger side... (good thing I'm the driver..lol) from what I've gathered you need to replace the center control stack..
http://www.cadillacforums.com/forum...92481-2008-cts-passenger-cooled-seat-not.html
http://www.cadillacforums.com/forum...92481-2008-cts-passenger-cooled-seat-not.html