Hello All....I love my car but the current problem is..
 

It won't start, today. I bought the Benz in Southern California last August and have kept it back home in Louisiana. But now I have just arrived back at school in Amherst, Massachusetts in JANUARY!! I arrived in the midst of the Blizzard of 2005(in Brooklyn). So, the car was buried and wouldn't start afterwards and I bought a new, big 850 cc battery. Its been starting better and quicker than ever before. But then this morning I go to get it going and the battery sounds close to dead. It won't turn over. Its doing that slow whirring like a crapped out battery would make. BUt that doesn't make sense because this battery is BRAND new and HUGE!

I think it is either one of two things: either I have a bad starter or something is draining my battery. I know that it isn't the alternator because I had it replaced in December before leaving New Orleans. Honestly, I wouldn't know what a bad starter would sound or feel like. No idea. On the other hand, a friend and I installed a cd player ourselves before right before i came up and there is a chance that it could be sapping power but I don't think so. We did everything by the book. The only other thing is that even without the key being in the ignition, i can hear what sounds like the battery humming or power cycling someplace (not the stereo or the ventilation), someplace that I have no earthly idea where it is!
I'M GOING CRAZY TRYING TO FIGURE THIS OUT! I PRAY FOR SOME KNOWLEDGEABLE GUIDANCE! HELP!

What model Mercedes ?
What brand of Battery,please (yes there are Bad Batteries in the world)
It sounds as if the whirring noise you described is part of the problem. Batteries make no noises like this. Maybe the antenna? If we knew the model it might help understand what else is involved.
In the meanwhile, recharge the battery fully before you do anything, if necessary take it somewhere that can do this on a slow charge. Fast charges are not "good" for a battery.
Welcome to the Forum BTW.

Sounds to me like something is sapping your power. Try pulling one fuse at a time until the whirring sounds you described stops. That might tell you what's running with the key off, and would be my first thing to check.

Good luck,

Chris

This is a posting from Todd Knutson from the MBZ.org list about dead batteries:


<sigh> Okay, here it goes. The answer is right here in one of a couple
steps. You'll need a voltmeter. Go from the start, and don't skip
steps. You'll know in 5 minutes.

0) No battery installed in car. Completely inspect the wiring to the
alternator. It must be all solid and tightly connected. Check battery
ground cable for corrosion on the terminal and frame connection. Take
the frame connection off if you aren't absolutely sure.

1) Charge battery. Fully charged batteries normally put out about 12.5
volts with nothing attached. Low point is 12.0 volts. Anything less
than 12 volts means a cell failure. Period. I know that a Mercedes
will start with a big battery only putting out 10.5 volts (one
dead cell). If we see 12.0 volts or better, move on to number two.

2) Connect battery to the system, and run a voltmeter with the key
turned off and no accessories or lights on. Check the voltage. If you
see about the same or a bit less, that's okay. You should never, at
all, drop below 12.0 volts. If you do, take the fuses out of the fuse
holder one by one until you find your voltage drop (open circuit fault).
Only the radio or clock circuit may make a small change in voltage.

3) With no accessories on, and lights off, start car. Check voltage.
Let sit for a couple minutes at an idle of at least 1,000 rpm. You must
register at least 13.0 volts, with a probable voltage of 13.4 volts
which is what your voltage regulator is set for. If you have less than
13.0 volts, see if you can get the alternator belt to squeal by blipping
the throttle. If not, you have a bad regulator.

4) With a reading of at least 13.0 (up to 13.4 volts) at 1,000 rpm,
start turning on accessories and keep monitoring the voltage. With all
accessories turned on, including lights, radio, defroster, you must have
at least 12.0 volts showing on your voltmeter. If you have 13.0 volts
showing on your voltmeter, there is nothing wrong. You have probably
tightened some cable enough or improved a ground connection. You'll be
fine.

5) Of course, you'll really see that you have dropped below 12.0 volts.
I'd peg this at 75%. I'm just screwing around here, since I already have
a very strong feeling that 1/2 of your regulator pick up brushes are
screwed. The regulator should have two pickups. If one brush has a poor
contact, like the spring or carbon hangs up in the sleeve, you will only
get a partial charging. This is very, very common. This is a one
minute trial when you have about a 12.2 volt charge with no accessories
and 11.0 with everything turned on. In short order, you've drained the
battery while you are driving.

6) I'm forcing you to read on. If you had total regulator failure,
you'd have zero charging. This would be obvious if you had the car
running and a voltage of 11.5 volts and dropping with no accessories.
Since you seem to have SOME charging, the rebuilt (um...did that come
from me???...I don't think so...I think you got a rebuilt starter) has a
defective set of brushes. Simple. If the regulator has that nice
replaceable pack (two Phillips screws or Allens holding a plate on the
back of the alternator) it takes five minutes and $50.00 to replace. It
takes an hour and $2.00 in brushes from the hardware store, but that
would assume that the problem is not in one of the holder sleeves.

Looks like a 1975 240D

Heavy Oils and Cold Climates can cause cold starting problems. What is your coldest outside temperature right now???...Bert

GLOW PLUGS!! Seems like you have some glow plugs out. I had a very similar problem with my 300sd and when I replaced the plugs and relay it starts perfectly.

low battery
 

Gotta find out what the noise is with the key out first. You may be able just to track to source by listening very carefully. If not try the pulling of individual fuses until noise stops. Unfortunatly very common type of problem. If noise remains constant while pulling all fuses one at a time think perhaps you should pay some attention to your cd player as it may be wired to a direct 12v source and only has the in line fuse at best. Good test right away is if it plays cds with the key out. :sun_smile Unfortunatly you will probably have to jump start car or charge battery as I suspect is almost going to be dead with this drain by tomorrow morning. Disconecting one terminal now may save enough power to locate the noise later. Let us know what it was when you find it.

I'm just gonna keep saying it.
If I save one soul the aggrevation that I went through, it is worth it.

Do not try to start a MBZ with a weak battery.
It is baffling how quickly you can fry the starter.
check the threads.....

This is really well done. However, I do have something to add. With a charged battery installed, disconnect a battery terminal and put your meter in series set to the highest current setting. If you see current draw, you have a significant short somewhere. If the indication is little or nothing, switch to lower current setting (could be something like 0-200mA range) Check again. The clock (if you have one) should be drawing something like 10mA. If you have much more draw than that, you have a problem. Remove and replace one fuse at a time, then do same with relays. If you get a sudden drop in current draw when you remove a fuse or relay, you have nearly isolated your problem. Leave that fuse or relay out and check to see what electrical device(s) are on that circuit.