How do you diagnose a 2002 Mercedes Benz C 240 to figure out what is draining the battery everyday?

This is a easy one, your seat control modules are draining your battery everyday! As long as you do have power seats correct? They stay awake and keep your c.a.n. bus awake which pulls about 1.5 amps or so until your battery is dead. These are not cheap control modules, but the only way to repair this is to replace them, and even though only one of the control modules is causing the drain, they both need to be replaced at the same time, or you will have more problems. Not to bad if you want to do it yourself, they are located under each seat and clip to the seat track. Just need to raise the seat and unplug them and install the new ones. Hope that helps!