1992 Mercedes Benz 124

DRIVER'S POWER SEAT MOVES UNEXPECTEDLY, WITHOUT DRIVER TOUCHING THE SEAT CONTROL BUTTONS. SEAT HAS FEATURE TO PLACE SEAT IN A "MEMORIZED" POSITION UPON DEMAND. SOMETIMES THE SEAT MOVES FORWARD, SOMETIMES BACK, SOMETIMES IN A ROCKING MOTION. APPROXIMATELY 20-30 SUCH INCIDENTS HAVE OCCURRED. TWICE, THE SEAT MOVED ALL THE WAY FORWARD ON ITS TRACK, CROWDING ME UP TO THE DASH AND MAKING IT DIFFICULT TO MOVE MY FEET. BEHAVIOR BEGAN THIS SUMMER AND SEEMS MOST LIKELY WHEN THE CAR INTERIOR IS HOT, FROM SITTING IN THE SUN. MOST INCIDENTS OCCURRED WITHIN A FEW MINUTES OF STARTING THE CAR ON A HOT DAY WHEN THE INTERIOR WAS HOT AT THE START. AT LEAST ONE INCIDENT OCCURRED AFTER THE CAR HAD BEEN DRIVEN FOR APPROXIMATELY 20-25 MINUTES WITH AIR CONDITIONING ON, AND INTERIOR HAD COOLED SOMEWHAT. (WEATHER HAS BEEN MOSTLY VERY HOT SINCE BEHAVIOR BEGAN, SO TEMPERATURE MAY BE A COINCIDENCE.) IN SOME INSTANCES, THE CONTROL SWITCHES CAN OVERRIDE THE SEAT MOTION, SOMETIMES THEY COULD NOT. USUALLY THE CONTROL SWITCH IS INOPERATIVE FOR SOME MINUTES AFTER AN INCIDENT. IN THE MOST SERIOUS INCIDENT, THE SEAT MOVED ALL THE WAY FORWARD, THE SEAT SWITCH COULD NOT STOP IT, AND THE SEAT CONTROLS REMAINED INOPERABLE FOR SEVERAL MINUTES. THE CAR WAS TAKEN TO THE LOCAL DEALER FOR REPAIR. THE CONTROL SWITCH WAS REPLACED, BUT THE PROBLEM CONTINUED. THE OWNER ATTEMPTED A REPAIR BY REPLACING THE SEAT CONTROL MODULE BENEATH THE SEAT. (THE MODULE STORES THE SEAT POSITION FOR RECALL BY THE MEMORY SWITCHES, AND IS THE INTERFACE BETWEEN THE SWITCH AND THE SEAT MOTORS.) THE REPLACEMENT MODULE WAS FROM THE SAME MAKE AND MODEL CAR, FROM A WRECKED VEHICLE. THE ASSUMPTION WAS MADE THAT IT WAS UNLIKELY THE WRECKED VEHICLE HAD THE SAME DEFECT. BUT THE BEHAVIOR CONTINUES AFTER REPLACING THE MODULE, SO EITHER THE CAUSE IS NOT THE MODULE, OR BOTH MODULES HAVE THE SAME FAILURE. INTERNET RESEARCH SHOWS MANY OTHER OWNERS HAVE EXPERIENCED SUCH INCIDENTS IN SAME MAKE CAR, IN THIS AND OTHER MODELS. *TR