MY C200 WILL NOT DISARM ONLY THE RED LIGHT IS FLASHING ON THE REARVIEW
MIRROR. MY LOCAL GARAGE SAID THAT THE KEYFOB IS FINE, SIGNAL IS STRONG
AND EVERYTHING IS OK WITH THE CAR BUT THEY CANT TRACE THE FAULT.
I hate to say it, but it needs to go to a dealer for diagnosis. If not, you will end up replacing parts that are good. A dealer is the only one that will have the proper test equipment to repair this issue for this car.
I wish I could give you a better answer, but there are many things that can cause the problem. I would be guessing.