AFTER STARTING UP THE CAR AND TURNING ON THE SEAT HEATERS WE NOTICED A STRONG BURNING SMELL. WE HAD JUST ENTERED A SLIP ROAD AND MY WIFE (WHO WAS DRIVING) FELT A BURNING IN HER LOWER LEFT SIDE. NEXT THING... SHE WAS ON FIRE! HER WINTER COAT BUST INTO FLAMES AND AFTER PULLING OVER I GRABBED HER OUT OF THE DRIVERS SEAT AND ROLLED HER IN THE SNOW TO EXTINGUISH THE FIRE, WE WERE AMAZED THAT THE SEAT HAD A LARGE BURN HOLE THROUGH THE LEATHER AND THAT THERE WASN'T ANY SAFETY SHUT OFF FOR THE SEAT HEATER INITIATED BY THE VEHICLE. AFTER A DETAILED DESCRIPTION TO THE SERVICE MANAGER AT THE LOCAL MERCEDES DEALERSHIP OF WHAT HAD HAPPENED,WE WERE TOLD THAT A $2578 REPAIR WOULD FIX THE PROBLEM... WE WERE AMAZED AT HOW UNCARING THEY WERE AND THAT THERE WASN'T A RECALL ACTIVE FOR THIS DEFECTIVE WIRING PROBLEM. WE WERE RELIEVED THAT THIS DIDN'T CAUSE ANY FATALITIES TO US OR ANY OTHER PEOPLE THAT COULD HAVE BEEN AFFECTED IF WE WOULD HAVE BEEN ON A FREEWAY AT A HIGHER SPEED.