I have not driven it in the last 2-3 months and the battery is dead and its located in the trunk. I can open the drivers door with the blade key but not the trunk. The key turns but the lid wont' open. How can I get 12 volts to the electrical system either inside the passenger compartment or under the hood so I can pop the trunk with the remote and jump start it? Is the cig. lighter always live or does the ignition have to be on for it to work? Is there a fuse box somewhere I can access?

 

IMO, too many bad things can happen to a MB that is totally dead electronically, you don't just jump start them, RTFM to see the procedure and follow it exactly otherwise I'd bite the bullet---tow it to a MB shop and consider it a lesson.

 

They have jumpers via cig. lighter...but it takes soooo long to start up! If you're willing to wait for it, I'd recommend getting some! I am no car expert, so let someone else chime in to make sure it's a good idea...I've seen it work from my car to a Civic, but I have a feeling those require a bit less to get started

 

This is no different than if you were to disconnect the battery when it is replaced. I just need to get into the trunk to jump start it. Is the lighter socket always live?

 

OPTION 1:
Look into your licence plate area, there is a place to insert blade key there to open the trunk. It is to the right of the trunk handle. Check manual - it explains exactly this condition.

OPTION 2:
you can jump the car via red terminal+engine and leave it jumped until your battery gets some charge.


I would just use the OPTION 1.

 

The cigarette lighter is not always live (by default). But I believe Mystro tried to convince you that you are not using the key correctly when trying to open the trunk, can you confirm that you did read the manual and followed the procedure accurately?

You can access live wires from the cabin too, e.g. remove all panels from the passenger footwell. If the battery is really flat, you cannot measure the hot wire, you would have to figure out the right one.

There are hot wires (from the rear battery) at the engine bay too even if not any obvious points.

 

You have to turn the lock on the trunk and pull the release handle, with the luck tumbler turned the trunk release is a mech release and WILL open the trunk.

Also, you do jump start from the red terminal and the exposed grounding post from under the hood. You SHOULD NOT try to jump start from aux battery. By the way, MB roadside is free for life for dead battery jump start....

 

You mentioned that it was totally dead..when you just change batts it
has the capacity to store important elect info but when it's totally dead and has been for awhile that's what I was referring to. I forgot about the roadside coverage but be sure and tell them how long it's been dead.

 

When this happened to me, I opened the fuse box on the drivers side of the dashboard.. And I believe that I gave some power to one of the fuses.. I think it was for AUX or the door locks or something of that sort... Then while giving it some power I used the trunk button to pop the trunk..

 

if all fail, you can always call MB Roadside assistant and they'll jump it for free. I'm sure they know how to get in the car. also, there is a jump start battery under the hood that you can get some voltage in.

 

There are notices in the manual that say NOT to use the AUX battery under the hood!!

 

Please don't use the aux battery to connect a jump start.

 

I just read the manual where it says there is a latch you lift after turning the key in the trunk lock. I must have forgot that.

 

I was able to open the trunk and jump start it. I'll have it on a charger overnight but it looks like the original MB battery and at 5 years old, I don't know if it will hold a charge.

 

5 Years is a good run... and a deep discharge like this further damages the battery. If you live in a winter/snow state climate, its better to proactively replace it now than get stuck in crappy weather.

 

ANSWER: Put the extra key from the keyfob in the trunk keyhole on the upper left side of the license plate. Turn that key and leave it there. Sit in the drivers seat. Pull the trunk release latch while turning the ignition. All 3 steps must be done. That's it. The trunk pops open.

 

Nice, you replied to a 15 year old thread, where OP already figured out the issue.