I work where we replace batteries only, and a Mercedes came in wanting a new battery..... now in the past they plugged in a 12v battery into the cigarette lighter, then removed the the "old" battery....Now this sounds so wrong to me....I believe it would damage the on-board computer.... but I DON'T KNOW FOR SURE... and that's my question... will that "really work"??? please help... I do have a mechanics background (only enough to get me in trouble these days...) any knowledge or help would be appreciated,
Thanx
Chris

 

The cigar lighter only works with the key on. If you keep the key off it will do nothing to have the 12v plugged in the the lighter. C-class have a spot to hook up a jump box right in front of the battery.( this is so you can jump start without removing the dust filter.) You can hook up a jump box here and you will not lose any programing. This will not damage anything. It also keeps the rear SAM for being damaged when a battery is connected.