Why does my Ford Explorer Blow only cold air from the rear vents?

Ok, so i have a 95' Ford explorer, eddy bouer edition, and my heaters only blow cold air from the rear vent, and the front vent's floor vent's or defroster's dont even turn on. What could be wrong with it and how could i fix it?|||You need to take it to a shop, not the dealer (they will charge you out the rear-end). Sounds like you have a bad switch.|||it has front and rear heater cores the one in the back has gone out...