Every so often the car stops working . The battery is dead, despite it being a new battery and having been replaced 2X in 6 months (Auto Zone NOT happy). The starter is fine etc. All connections to the battery have been checked and are fine etc. Car is housed in a garage but could dampness be shorting out a fuse?....and which fuse would I check? or is there some innate electrical problem that I am not going to solve? We charge up the battery and the car works for another 6 weeks so what is draining the battery. I am also the original owne.

you would be advised to talk with an accredited auto electrician on this
if the regulation is done in the ECM unit then you will not be able to by pass and fit an external regulator
if it is possible then just get a regulator from the wreckers /junk yard and have it wired in

if this is a what I refer to as newer model vehicles 93 to 95 and up if you disconnect the battery cable while it is running it kills power to the computer and the car will shut down, it can also fry the computer. That is something that you could do a really long time ago, but now can cause expensive damage. I would suggest taking car to Auto Zone or Advance. let them check the battery and alternator even though they are new.. I cant tell you how many new alternators fresh out of the box I have installed and were defective. same can go for batteries they sometimes can sit on a shelf 6 months before being sold and can start to break down and they will not hold a charge. if they both test ok. you need to check for a parasitic drain. I believe Auto Zone will do that for you for free like the battery and alternator test. if not take a multi meter,,put leads on battery and see if voltage is slowly dropping over a period of an hour or two. then you can start removing fuses one by one and see if voltage drop stops.. if say radio fuse stops it,, you know there is a short or problem with the radio,,

Yes, it is totally normal for your Mercedes battery to go dead after 4 weeks of non use due to the onboard computers that drain on the battery. I store my Mercedes for up to 5-6 months at a time. The solution is to install a battery tender that plugs into a power outlet in your garage and this will maintain proper charge in the battery and then will shut itself off until the voltage drops below the threshold again , then will kick on and bring the battery up to full charge. Any auto parts store, ie. Napa, Auto Zone, Pep Boys, etc. carries them. Cost is approx. $35-$45 and take the average person 1/2 hour to install.

If the red light that stopped blinking is on your dash board, then your car battery is most likely dead. All the problems you mentioned above happen when the battery is bad or dead. Auto Zone will test the battery free of charge to see if it's still good or time to get a new one. They will also re-charge the battery if it is good. Check to see if your battery posts & the connection terminals to it are clean & tight. If there not..... then your car's charging system can't re-charge it. Also have Auto Zone check to see if it's the RIGHT battery for your car, & have them test your alternator. There all free services Auto Zone does.

Get a cheap multimeter and test for drain, sometimes it is the starter, check the battery at all off, and running, your parts I hope are warrantied have them both tested and checked, The starter and or coil can cause weird electrical issues and a bad ground could be causing everything to work harder. You need an honest mechanic who cares about solving the problems.

Take your battery to a auto supply store such as auto zone / advance Auto / pepboys these stores will check your battery for free, most likely your problem is you have cells dead in the battery,one cell being dead can make a battery not charge all the way.
Most batteries are good gor four years IF you are one who does not do any maintenance

The charging circuit/voltage maybe faulty.
I recommend you get an auto electrician to check out your alternator and charging regulator.

if its not charging while running at14.5 volts or so you have a charging problem mabey no power to the alternator if its charging at 14.5 or so and the batery load tests good and its going dead over night you have a draw from some component in the system.

when your ready for the repair and have the money have it done. but the rear seal fix from auto zone will work for a bit it will do two things it will either stop it or slow it down a lot.

The batteries they put in the trucks from the factory ****. I went through 3 of them under warranty, they lasted 6 months a piece.

I did research to find who made the factory model. I found an alternative manufacture and bought their battery and I have not had a problem sense. I bought a Duralast from auto zone.