Mercedes ALARM CONTROL UNIT Up for sales is good used Mercedes Alarm control unit. This fits many mercedes models. A failed will cause a whole host of alarm related problems, from random alarming to total non functioning. this is also a good part to keep as an extra! they are well over $350 from MBUSA... The Mercedes part number on this unit is 1268200826, also fits 1268202426 Best bet is to check the part number off your old relay. These are located under the passenger side floor carpet. I only sell the OEM units, never aftermarket so they are the same quality as your original. Thanks for looking!