Moin, Mein alten Sprinter (BJ 2005 ) has for some time the problem, which slightly in the parked condition the battery sucks empty. The radio is meanwhile expanded – now we have the preheating in suspicion, which just recently turns on unmotivated. Permanently when parking the negative pole of the battery is also not a solution. There is due to the age no proof of use for this car. How do I adjust the preheating reasonably? How do I find the error i n the electrics? I am a DAU (the stupidest user to accept), but the whole screwdrivers also did not know any advice…. I hope for an answer ; thank you in advance