Yikes! I left my 2000 S500 for a month. Upon returning, it won't start, and is completely shut down. Key won't turn, trunk won't open, etc. Recently had lots of electrical work and was working great. Want to jumpstart it but can't get into the trunk and cig-lighter jumpstarter won't work either. Any ideas?

 

Cigarette lighter adapter from a battery charger (not a jumpstart kit via the lighter outlet) should work to charge the battery enough to start if you leave it to work for an hour or more. Unsure why your trunk will not open manually with a key. If you do getthe trunk open, suggest you disconnect the battery cables and charge the battery. Although sometimes battery jumpstarts will work ok and no issues occur, there is high potential for weird, odd electrical problems to subsequently occur following a dead battery jumpstart on these MB cars. I know from experience. There are a couple other emergency options if you can not get anycigarette lighter to be functional withkey off and no access to the trunk.
Let me know.

 

A question that must be asked is ...Why is the battery flat?

How old is the battery?
What is the useage pattern of the car? Batteries don't like being left unused.
Is the car locked at night etc.

These cars are a bit too clever for their own good and as has been found with other members of this site leaving the keys in the ignition etc stops the various computers going to sleep and the battery drains as a consequence.

Oh... and since the battery is flat you will need your radio code to get the radio working again once power is restored. If you do not have this code (or it is incorrect0 you will need to get MB to get the code for you.

Stuart.

 

just open the trunk with mechanical key and charge the battery.