DIY: Open trunk with dead battery
 

Dead battery? Can't open the trunk with the metal key?

Open the hood, take off the plastic cover which holds the ECU and the fuse bar. There's a clip that holds the fuse bar in place push that aside and pull the fuse bar up. There should be a big thick red wire that attaches it self to the fuse bar that runs directly to the battery and other accessories as you can see in the picture. Disconnect it from the fuse bar and attach your positive jump lead there and attach ground lead on the body at a main ground. Use your key or use the door latch button on the door. Volah! Trunk opens.
http://img845.imageshack.us/img845/9569/wire.jpg

Thank you for the information.

Actually, this should be put up as sticky.

That is good to know. I had this happen to me but used the battery cable jumper leads under the passenger foot well. Pull carpet back, remove floor plate hook up jumpers, as I recall.

This worked
 

Just want you to know that my battery went completely dead. I used this method in you photo and it worked. I popped my trunk with my remote and got my battery out.

Great post!!

Had to use this also. Took me quite some tine to figure out that the contact is on the passenger side not the driver's. I have since started carrying a jumper pack. I've been wondering if I hook the jumper pack 12v cigarette adapter output to the cl65 lighter if that would energize the trunk?

Anyone else seen this
http://www.qsnm.info/xiaowang1.jpg
http://www.qsnm.info/xiaowang02.jpg
http://www.qsnm.info/xiaowang01.jpg
http://www.qsnm.info/xiaowang2.jpg
http://www.qsnm.info/xiaowang0.jpg

Although supposedly I have the correct metal key, the first time I encountered this issue that the key could not turn, I inserted the WD40's plastic nozzle into the key hole, sprayed a good amount, waited a while and bingo! Now, since the key mechanism faces down, the lubrication falls out the key hole, I spray it every two or three months even if the key works.

I know this is an old thread but I'm having this issue now. Battery dead, I had the trunk open with the key but it closed itself and won't reopen. I've got 2 fuse blocks under the hood, one on left and on on right. I can't get either block to come out and I don't want to force anything, I'm worried I won't get it back in. Can I get power to trunk opener through the cigarette lighter socket? Don't know why Mercedes didn't put a Positive terminal under the hood with an easier access.

The fuse block on the passenger side worked for me although key is much easier. If you google someone posted a web page with photos.