2 days ago I replaced my older battery for a new one...yesterday used car for a 14 mile round trip and no warning no lights til first 5-6 miles it showed battery/alternator workshop(red display) but engine was still running but as I slowed down or got a stop warning fully gone...when I started driving warning came back..I was in Walmart parking lot then so I drove slow til I parked when I turned off car then turned it back on all was clear...was in store 30 minutes returned to car turned on no problems so started driving after a few seconds driving the bat/alt warning came back..funny thing is when I stopped car had no warnings as I started to move I had warnings. So I drive car and noticed my gear stood in first so I looked and was in M mode..I tried to put it back in D but unless I was doing that wrong it wouldn't go to D...I drove back in M and still had warnings but little by little more warnings show up and I wasn't given option to shift...I had to drive slow but was fortunate I had made it to farthest entrance of my subdivision so slow was possible...since it wouldn't shift to 2nd or third I stop car and shut it off then back on....when back on I decided let me run car slowly in 2nd but the revs didn't seem to be in 2nd...I eventually made it home slowly but by time I parked car in garage a coolant temperature warning was on I turned of car...waited 45 minutes went to turn car on and no warnings nothing at all even car temp was ok which 45 minutes shouldn't have cooled already..anyways I noticed after short while batt/alt light came on...baffed turned car off then on...still warning opened hood tightened posts a little more then stopped for day...I bought a post cleaner so once home went and took positive first off then negative..cleaned them then re-installed them..went to turn on car but remote doesn't open door..it appears Batt dead which baffles me because car turned on no problems yesterday..I should have tested car prior to messing with battery but didn't so have no idea if anything I did today caused it to be dead or appear that way...It's hard to say alternator when car turned on no problems yesterday...it almost seems like car has a draw of some kind when off if Battery is dead...I'm sorry but no volt meter and one I ordered is a long way from getting here. I just entered car with key fob insert and yep battery is dead................how can that be when car turned on no problem yesterday? For a new battery to go dead when car off I would presume there is a draw on the system but what could it be?

I have read bout the seat adjusters pulling power.

::CORRECTION::I had THE SEAT HEATER issue once it was fixed...but gonna find fuse for it and take it off as soon as I can

Ok I jumped car yesterday and left it on charging off alternator about 10-15 minutes turned off car then turned it on again from battery and started fine. I turned it off but left a charger on it rest of night and checked this morning while charger on and car is dead. Now I know some want to blame a faulty alternator but if that was case then car should have not restarted again without hesitation after 10-15 minute of leaving car on. But anyways since car did turn on just on battery after 10-15 minutes I decided to leave charge on it overnight and checked this morning and though charger was on car is dead. The car had started last night no problem but dead now. Leads me to think something is drawing while car is off at such a rate that charger can't maintain or further charge my 3 day new battery. What when car off can draw that much if faulty?

could be that the battery is DOA. unhook the battery and charge it. Then let it sit overnight. If it has lost voltage it is the battery.

Well it's most likely faulty alternator....after jumping car I removed positive post from battery and after a few minutes it died so alternator looks to be issue and nothing else...well atleast til alternator replaced. Thanks for replying

How would you explain the loss of voltage with the car off?

I don't know but it could be my amps or radio requiring some power to maintain memory or something IDK but until the alternator gets fixed it's not gonna be known. I'll get alt replaced and take it from that. I'll report if this issue still exists after

Well checked out voltage with voltmeter with friend after reconnecting battery and car started right up after fixing a blown fuse to fuel pump which I have no idea why it blew to begin with. Anyways battery never drain cause I had positive post disconnected and once reconnected car did start right up the voltage with car off was 12+ when car on at times 14 or mostly 13.8 no warnings except batt/alt workshop...tested voltage draw when my radio with amps on and voltmeter was constant 14+ even reached 15...added all interior lights and AC full blast and voltmeter still show 14+...only warning on average was batt/alt workshop. I then took car for a spin and very shortly from leaving garage all sorts of warnings came on no light sensor no esp brake-light L and R etc...car though in D wouldn't shift so parked and checked voltage again and still 14 so weird I mean I know car draws to use the power-train but how come warnings but voltage still within what's needed? It's parked now and battery fully charged but removed fuse to my amps incase thats the reason why battery went dead. If it goes dead then something is killing battery while car off...my thing is is it still the alternator though it has constant 14 when car on?

BTW my alternator was replaced about 3/4 years ago from a valeo to bosch....upon reading it says valeo don't have replaceable regulators but the bosch does....it seems voltage regulator may be going based on warnings so I'd like to replace it first..is it something that requires pulling out alternator? or can it be replaced by jacking up car?

Ok car battery dead again this morning even though last night I started car fine no hesitation at all...so to me it's not the alternator because even when I removed positive post car stayed on atleast 1.5 to 2 minutes and if alternator bad it would die fast. As I had already written in earlier post voltmeter was consistent 14+ even when load applied thru radio, amps AC running max all interior lights on etc. To me something while car off is drawing a slow enough rate that it kills battery overnight..does anyone have suggestions what to remove first? I'm thinking seat movement controls then seat heater control.

Unplug the both seat control modules under each seat and see what happens.

I just jumped car and unplugged both sides seat control and I believe heat element control thus 2 plugs both different sizes from the other then pulled overhead console fuse #9 from rear SAM. I still get battery/alt workshop warning. I know alot of weird stuff happens when batt/alt problem is an issue...Alternator may still be culprit for that but battery drain shouldn't occur any further when battery is fully hooked up to car...gonna check later and tonight if car turns on to atleast prove battery isn't drained. If car turns on in the morning then either heating element/s or seat/s control or the overhead console is faulty. Among the warnings I get are no turn signal,battery/alternator workshop

here is plugs I pulled

Well checked battery this morning and car dead even with though over head console, seat control and heater element unplugged. Now with all these devises unplugged I fail to understand why battery dead though car turned on from battery no problem last night...now I'm wondering if it is possible if alternator bad even though car off that somehow it's causing enough draw to kill battery overnight??


EDIT over head console fuse pulled not unplugged

So how about removing one of the battery posts at night when you know the battery is working and then reconnect it in the morning to see if it will start. It might be a bad battery that won't hold a charge for 8+ hours or so.

Also hook up the voltmeter with long wires so you can have the meter in the car while driving it. Then you can see if it still reads 14V when the visit workshop message comes up.

Actually already done that and it's only time it actually held a charge overnight and would turn car on no issue. I was instructed to charge battery then remove connector from rear of alternator to isolate it from battery but rest of car will still be able to drain it. Battery only a week or less old so I can always replace it no problem. To me isolating the alternator from battery will show me if it's alternator and not seat heaters nor seat control or over head console which didn't cause the battery drain this time since all were off one way or another

Ok. So car was fine until you changed the battery. Take it back and replace it. Battery may have a bad cell. If it is the only thing you changed then most likely the problem. If you changed the battery because of issues than need to start somewhere else.

Car due to that 1 year on prior battery for storage in winter I didn't start it nor hooked it to battery tender had the Batt/ALT workshop warning but everytime til recently the warning would go away and stay away for days if I don't use car but always started right up and charged so this time to finally stop that I replaced battery. I doubt battery is issue as posted before it has 12v average when car off and constant 14v when on and even with heavy load still stayed 13.8v to as high as 15v+

a little bit OT, but did you get this after you jumped started your car? i recall a while back that there was some thought that jump starting the car (not sure if w203 specific or a mercedes thing) can lead to blowing fuses/the rear SAM. ever since I read that a while back, i've only used a trickle charger if i had an issue requiring a jump.

I believe yes but ok now

well progress is slow cause I need help doing the hands on stuff but yesterday I charged battery thru having car on maybe 25 minutes...turned it off and removed positive post from battery that connects it to car...I briefly reconnected positive post without tightening it this morning and turned on car no problem then turned off car and removed battery post. I was just trying to prove battery isn't bad. Maybe today my friend will help me by removing the connector from rear of alternator that goes directly to battery this will prove if there does exist a drain from battery to car. I reconnected the plugs to under seat seat control and heater element as well as replaced fuse in rear same for overhead console. If once I get connector from back of alternator off and if battery don't drain then only fault left will be at alternator.

this might seem like a stupid/silly idea, but a while back i was having an issue where my car would lose power overnight and i disconnected my seats (didn't fix it), got a new voltage regulator, then a new alternator, new battery...none of that fixed it. my buddy had this idea that maybe i had a bad ground and he essentially created a new ground for the price of essentially a piece of speaker wire. it has since been upgraded to better wire, but it resolved my problem and i no longer had that issue. it was a cheap easy fix. maybe give it a try? here is what it looks like now on my car

First your avatar pic

I am willing to try anything prior to buying and replacing the alternator...can you take exact pics from where to where?

lol. glad you like it. here ya go









i added a red line in the last pic in case you can't trace the route of the wire. i basically hide it a little bit below the battery cover b/c the wire was a little bit long.