My 2007 R-350 is dead...
 

I left the key in the "ON" position all night (after quickly turning it on to open the garage door). Now it is dead - can't jump it or turn the key in the ignition. We've tried both electric keys - neither will work.

Any thoughts? Or do I just call Roadside Assistance? I'm stuck at home until it's fixed.
Thanks!
JP

Disconnect the battery and use a charger. Call a taxi and go to an auto store like Pep Boys or Autozone but call ahead to make sure they have one.
Let the battery charge then carefully reconnect the battery to the car.

You can also call roadside assistance for a new battery. It will cost more, but it is a better battery than you will get from the big-box chain stores. The roadside assistance person will also install it and synchronize your car. Be sure that you have your radio card with you.

Thanks for the quick response!
So the battery is gone? Can't be jumped? One more question - Radio card? Not sure what that is.

Roadside assistance will come out and install a new battery for a little over $100 - and the MB batteries are typically better than the crap you get at the big name auto parts stores. The original one in our old ML320 lasted 8 years.

Don't jump-start the car without also charging the battery. The charging system is not designed to bring the battery back from no charge while also running the many, many electrical systems in the car.

You may want to disconnect the battery and put it on a charger overnight; this is certainly what I would do first. Your battery isn't that old, and will probably live. Had you discharged an Auto-Zone battery, on the other hand, your chances would be much lower.

Once it is charged, reconnect it and synchronize the car (as per the owner's manual).

The radio card has the key code which must be entered if the power to the radio is interrupted. Do not guess at the code, because if you get it wrong a few times, it will lock you out and may require to be powered on for a significant period (this should be addressed in your radio manual).

The battery is just dead, you don't need a new one you need to get it charged.

Call roadside assetence and they will send someone out to give you a jump. Drive the car for a bit once they get it running to charge the battery up good.


The number should be on the inside of the glove box door.

Actually fully draining a battery like that does do permanent damage to it....it'd be better to just get a new one most likely....or charge it back up and not expect it to last as long as it would have....I suppose its worth a try.

It depends how far down it's voltage got. And we don't know. If we had a voltage reading on it then we could fathom a guess. Those factory batteries are pretty good so I would give it a good chance to be resurrected in this case.

FWIW, MB has been using Absorbent Glass Mat, or AGM batteries for several years now. They behave differently than traditional lead-acid batteries. Take a look at the battery chargers available nowadays. The better ones have a setting specifically for charging AGM batteries.

Charging a stone-dead battery until the vehicle can be started without assistance is always my first choice, but go ahead and jump-start it if this isn't possible. My Roadside Tech's do a few dozen of these every month with virtually no problems.