Thought this post was buried, so my apologies for double posting. Here is where I am at currently:

This winter my battery started running out of power if I left the car sitting for a day. As long as I drove the car the battery would have enough power, but if left sitting for a day it would not start, 2 days and the battery would be totally dead.

I took it to the dealer who could not figure it out, they replaced the battery and told me to come back if it still discharged. They said the alternator and charging system checked out OK. Of course it kept doing the same thing.

I took it to my independent shop and he checked for a draw, which he found. He said it was about a 4.5V draw. He did pull the fuses one by one and said he found no problems, including the radio. He checked the alternator and the charging system and they were OK. I do have an aftermarket radio, but this was installed over 2 years ago and has never given me a problem. He did check for any dummy lights, etc. that might stay on when the car is off.

His best guess is something that is not fused such as a lock deicer or a side mirror heater. I am bringing it back to him this week for more diagnosis. I also asked him to take a good look at the positive battery cable for corrosion or grounding.

Basically both the dealer and my indie are completely baffled by this. Does anyone have any kind of suggestions or experience with this? I am going to have to put one of those battery buddies in, but I really would prefer not to and to have the car run the way its supposed to.

Thanx much.

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2007 Corvette Convertible Torch Red
1996 MBz SL500
2008 Harley Davidson Night Rod Special

In addition to what I posted on your second post, I would not expect a technician who quantified a draw in voltage to be able to fix it. Voltage has no part in the situation. Current causes batteries to die not voltage.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

You start off saying this is a "wierd" problem, however, in my 1 year experience on this site I have seen this complaint many times, and there were always many helpful replies from many people who had the same problem. Since you have more posts than me I assume you have abserved the same thing. So it is a common problem. And a search should also reveal this. And most of the threads go the same way, with lots of specific advice given and most of it ignored completely. The problem is most responders assume the person is looking for instructions on how to troubleshoot their car when they are actually looking for the "Psychic Hotline". Well, the psychics have chimed in with the ususal listing of: Alarms, lights, and radios. I have learned a couple of things from this thread: Check the trunk light to see if it is warm, check the alternator to see if it is warm, and Steve's very good (as usual) advice about hooking up the ammeter before disconnecting the battery.

There are 2 ways you can go with this thing: Try to learn about it and fix it yourself, OR: get someone else to fix it for you. So far it looks like you are going with plan "B". The problem with plan "B" and the reason I would rather get my teeth drilled without novacaine than use plan "B" is just what you are experiencing, "Everyone is baffled". Well I believe that if you drove to Steve B's shop that he would have it figured out in no time. Basically if you are going to use plan "B" then you need to find better help. It is my observation that many professional mechanics are not experts on electricity. You need to find one that is, or at least one who will follow the instructions given here.

If you want to try plan "A" then go get a meter and do the tests spelled out in these posts. Otherwise find another mechanic or, Plan "C": Drive to Florida. I recommend Plan C.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

I have done an exhaustive search on these forums, as well as google. I have had the car checked by both a local Mercedes dealer as well as a foreign car electric specialist. I have taken the advice of other posters and have checked (both myself and the shops) the alternator, alarm, lights, trunk light, radio, etc etc etc. I am not looking for a psychic hotline, nor am I particularly looking to personally troubleshoot this. But when both a Mercedes dealer and a electric shop are baffled I would hope someone on here would have seen this before.

How I wish I was close to someone like Steve to have my car diagnosed, unfortunately I am in the armpit of America out here (also know as Massachusetts), and it is a bit tough to find a good shop. The dealer seems intent on replacing entire systems as opposed to diagnosing specific problems.

So I am not sure if you are complaining about my question?

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2007 Corvette Convertible Torch Red
1996 MBz SL500
2008 Harley Davidson Night Rod Special

I am not complaining. I am just saying that in my opinion this subject has been beaten to death lately. I have seen it several times. There was even one recently where someone offered to drive to a lady's house to fix this for her!! (She didn't take them up on it). Admittedly, the search function on the site is not always the best and there would be great benefit to some kind of subject indexing function, but the software is canned, so will not be changed. Bottom line: You need to find a different shop. Maybe someone can suggest one in your area. As far as someone here having seen this before, there have been many responses from these people with all the different causes they listed, including some I never heard of before like the alternator field winding. Maybe it is one of these things, or it could be something else. I was a bench tech for 6 years working on the same controls over and over and it always amazed me that I rarely saw the same exact thing twice, even after 6 years. To find the problem you have to go from A to Z. I good tech can do this. Others can only shoot in the dark.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

My friend's American made car had the same extact problem. The battery was fine and the altenator charged up perfectly when tested. The problem was with the diode in the altenator. It drained the battery after couple of days of inactivity. When they first tested the alternator they only checked if it charges. AutoZone can check if the diode is faulty as long the altenator is still hooked to the car. He changed the whole altenator and the car runs fine now.

They might already checked for that considering you took it to MB dealer but I thought it never hurt to mention it.

I once had a flakey regulator in the alternator do just that......drain the battery on my car overnight for no reason.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche