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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4265
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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Marty only.Different email, but same guy.Replaced M relay

Customer Question

Marty only.Different email, but same guy.Replaced M relay and car now starts. Approved payment. Now for the original issue. Battery drain.2010 Mercedes E350Takes about 5 to 7 days and battery is so low that it has to be charged to crank, otherwise just 'clicks'.Removed negative cable from battery and measure 4.5 amps from negative cable to negative battery terminal. No key in ignition, everything off.Removed all fuses from fuse box in engine and no change to 4.5 amps.Need your advice on how to find, fix the battery drain.Thanks -David
Submitted: 1 year ago.
Category: Mercedes
Expert:  Lou P. master tech replied 1 year ago.

Hello, i noticed your question has not been responded to yet, i have diagnosed and fixed many battery drain issues in my 16 years benz dealer experience especially in your w212 that has had multiple issues causing battery drains, would you be willing to work with me ? Lou P.

Customer: replied 1 year ago.
Let's do it.
Customer: replied 1 year ago.
By the way, get this fixed where I do not have to replace a seat module or other expensive electronic device and I'll tip you nicely. Electrical engineer...that's the bad news.
Expert:  Lou P. master tech replied 1 year ago.

lol, straight to business huh lol , ok, so here is what we need to do first, you caught me right before i was about to sign off, so here,

close all the doors and engine hood and open the trunk and latch the latch manually with your finger or a screwdriver, lock the car, very carefully hook up you ammeter or amp meter what have you while separating the negative cable from the battery so you do not set the alarm off, then you have to wait 45 min for the electronics to "sleep" then and only then can you accurately read the draw. once we determine the draw, we will redo the battery open all the doors and hood and do the same and manually latch them ( or you can start with this as well either is fine) then lock and wait 45min, then we pull one fuse at a time and only one, never pull them all out that will cause more headache down the road, (oh crap you said the E word...... ) :) no worries, ok so again we pull one fuse at a time and wait about 5 seconds for a change and if no change reinsert and move to next one. you have a fuse box in the engine bay left side, on the side of the dash left side and maybe right side i have to refresh myself and a fuse box in the trunk. lots and lots of fuses so be patient , that should be enough to arm you with ammo to see what is happening. and most likely its a radio component or seat module. but first we need to establish the amount of draw. under a amp and its going to be easy, over a amp and it can get fussy because a module can have 2 fuses in a separate fuse box and stay awake and wake up the other modules to cause a big draw .

let me know how this sounds i will await your reply before i sign off, Lou P.

Customer: replied 1 year ago.
Sounds good. You obviously know your stuff. I was concerned with sleep mode. Go to bed, talk to you soon.
Expert:  Lou P. master tech replied 1 year ago.

lol yes sir.

here are a few links to the fuse boxes. not a whole lot of help but it may

do not be concerned about the prefuse boxes at this time. you may like to have that info down the road. have a good night , Lou P

Customer: replied 1 year ago.
My battery is under hood. As I read, it appears your instructions indicate my battery is in the trunk?
Expert:  Lou P. master tech replied 1 year ago.

doh, sorry, autopilot. the e350 was in the engine bay, the e550 v8 was in the trunk. so yes. you are correct under the hood.

Expert:  Lou P. master tech replied 1 year ago.

https://www.mediafire.com/folder/uh14bl7hbsnbl/212

here is a file i made . now i am signing off, have a good night, Lou.

Customer: replied 1 year ago.
Good morning Lou. I do have a couple of questions before I begin. Does the hood have a latch that must be manually latched so the car can sleep while the hood is open? If so, where?Please note that the car sits in our garage all night, usually around 12 hours which is when the majority of battery drain occurs. We NEVER lock our car when in the garage. Should I be doing the current readings after the car goes to sleep with everything lock as you have described above or should I leave the car unlocked as it goes to sleep?Last question. I understand opening the hood and all other doors and trunk being closed, remove negative battery terminal while multimeter is connected and then waiting 45 minutes to determine battery drain current. What I don't understand is then repeating this measurement with doors and trunk open (all are manually latched to simulate everything is closed so it can go into sleep mode)? Is that just to get physical access to the car as I pull fuses. Not understanding why the doors/trunk needs to be open when taking the second set of readings.I warned you-engineer. Best.
Expert:  Lou P. master tech replied 1 year ago.

ok so

( I understand opening the hood and all other doors and trunk being closed, remove negative battery terminal while multimeter is connected and then waiting 45 minutes to determine battery drain current. What I don't understand is then repeating this measurement with doors and trunk open (all are manually latched to simulate everything is closed so it can go into sleep mode)? Is that just to get physical access to the car as I pull fuses. Not understanding why the doors/trunk needs to be open when taking the second set of readings.)

yes , just for physical access, thats why in my post i said you can just do the measurement with the doors and lids open right off the bat, i just wanted to confirm a draw, so i should have just deleted that sentence of testing the draw with the doors closed, my apologies, and to latch the hood latch just press down on the catches on the radiator support, if you look under the latches you will see a metal strip that activates the microswitch, there should only be one on the passenger side but there may be one on the drivers side as well. and no worries please ask i want to be on the same page, im actually happy to work with an engineer because you have the training and mental thought process that will help me help you. and yes always lock the car for the test, that way it forces the car to sleep, if you dont lock it it will still sleep but at a undefined time.

Customer: replied 1 year ago.
Thanks Lou. Enjoy this process and most of all, learning! Won't get back to you until Thursday evening due to my schedule. 7 Mercedes, 4 drivers.Always something new to learn.By-the-way, did I 'hear' you say that locking the car overnight in the garage could potentially mitigate (not fix) the battery drain issue? Mitigate: the problem is there, but because it goes to sleep in 45 minutes as opposed to 'who knows when' (unlocked) the daily alternator charge will keep the battery at a charge level that won't see a significant battery drain? Even if so, I would want to fix, I am a n engineer. LOL
Expert:  Lou P. master tech replied 1 year ago.

i tried to find the quiescent draw info for this model, mercedes has not added it to the info for some reason. i have it for other models but not for this one. also if you have that many you may want to look into purchasing a scan tool

www.mbstarshop.com

your model actually will tell the scanner what was left on or caused a drain within reason, it has a battery sensor on the negative cable of the battery that tells the amp draw.

and no, locking the car will not fix it, the car unlocked should still not draw past 1 hour of being undisturbed. if not the rear sam control module will kill off circuits to stop the draw, so whatever is happening i think there is a module that is keeping others awake.

Customer: replied 1 year ago.
I could get access to a scanner, but I'd rather learn and
'smoke' this out. Pulling fuses on the agenda....
Expert:  Lou P. master tech replied 1 year ago.

gotcha. just throwing some info out there.

if you pull a fuse and the amperage spikes then give the car a good 5 minutes once reinstalling the fuse to go back to rest, also keep the key handy on you , the alarm may go off when you pull a certain fuse. not sure which one or if it will happen but its good practice to keep the key on you.

Customer: replied 1 year ago.
When I pull my wife's fuse and emotions spike, it takes way more than 5 minutes to go back to rest; hense, I love working on cars. But then, physical access to cars is not as rewarding. Always the 'balance' in life that separate the men from the boys....
Expert:  Lou P. master tech replied 1 year ago.

haha, i dont have a fix for the wife, i been working on mine 12 years, hardest diagnosis ever. and yes balance is something few can master, years of practice. no manual for that one.

Customer: replied 12 months ago.
Car in sleep mode and current fluctuated between 8 and 27 milliamperes. Rapidly jumping from 8 to 22 to 25 to 8 to .....Rapid: fluctuates in less than half a second. Constantly changing values. Yes, milliamperes.Ok, I'm lost. Did not pull any fuses because there was not a steady current drain. Thoughts?
Expert:  Lou P. master tech replied 12 months ago.
That is odd. Very odd. Explain to me the steps you did in detail and also is your battery new in your meter ? Do you have a second meter ?
Customer: replied 12 months ago.
Brand new meter, but I will try a different meter tomorrow.Step 1: lift hood and manually latch hood
Step 2: lock car with hood open
Step 3: wait 1 hour
Step 4: remove negative battery terminal cable very carefully while having ammeter leads on battery terminal and battery cable. Very careful not to 'break' circuit with battery cable now completely removed from battery terminal.
Step 5: read currentI will repeat tomorrow with different meter.Love these kind of issues. This really seems like an operator error cause nothing else makes sense. Go figure: engineer operator!
Expert:  Lou P. master tech replied 12 months ago.
Yeah you did it as I would have. I do question the meter. There is a small possibility that a module is causing the slight fluctuation. But I can't remember a draw that I have had where I xperienced that. So get s other meter or test another car as a control to see if the meter reacts the same or not. Have a good night. I also like problem cars. Some made it so we should be able to fix it.
Customer: replied 12 months ago.
Before going to bed last night:
1) hood open and manually lathched
2) car left unlocked (what we normally do overnight)
3) this morning remove negative battery cable same as previously.
4) 5.0 milliamperes with no fluctuationThis is two low of a current to cause battery drain. Oh, same multimeter - it is brand new.Yesterday afternoon, before any testing, I got in the car and I was suspicious of the driver seat lombar adjustment. No reason, just intuitive which means nothing. I played with it to see if if was stuck. No issues, it worked fine.Not sure if that had an effect. I will take another read later today after locking the cat and letting it sit for 45 minutes. See if I get a repeat of the flutlctuactuon readings I had previously.
Expert:  Lou P. master tech replied 12 months ago.

ok, what meter are you using? brand and model?

Customer: replied 12 months ago.
Craftsman; model 82141I have two other meters. I'll take another read tomorrow with other meter.
Expert:  Lou P. master tech replied 12 months ago.

ok just to be on the same page, the meter should be set to 10A dc and the red lead in the left grey 10A port and the black lead in the center.

i dont like to assume you know how to use the meter engineer or not , everyone makes mistakes. i have seen a guy chase a draw for days over a dead battery in the meter , also a guy chase a draw because he had it set to volts and the car never even had a draw lol. just want to be on the same page. i never mean to offend, i am not near you so i need to know everything and step that is happening as if i were. i wont be on a whole lot this weekend but i will still get emails when you reply and will reply as soon as i can. so give me some leadway with my responses please and hope you enjoy your weekend and dont spend it racking your brain on the car :)

Customer: replied 12 months ago.
No worries on you being away this weekend. Enjoy time away and we can catch up when you return.Meter use. Thanks for making sure. I was a high voltage testing engineer in my younger days, so I get what you are saying. No issues, I am using the meter correctly.
Expert:  Lou P. master tech replied 12 months ago.

good deal, here is a list of the things we would do to your model E class when it came in with a dead battery and suspected battery draw, your model was a pain in the arse, because there was not 1 dedicated fix and engineering kept having us do all this work and some models still ended up having a draw , here is what we had to do.

Expert:  Lou P. master tech replied 12 months ago.

here are the acronyms

  • scn - software calibration number - coding automatically performed via the diagnostic machine to the germany central server, they took away our options to code modules for the most part.
  • KG- keyless go (push start keyless start)
  • ACC - automatic climate control - ac control head control module
  • IC- instrument cluster
  • SAMR - rear sam with fuse box - sam - signal acquisition module, responsible for all rear electronics
  • SAMF- front sam and fuse box- responsible for all front electronics
  • BNS- battery sensor on negative cable.
  • LIN- local interconnect network- a dedicated 1 wire communication wire
  • EIS- electronic ignition switch
  • SDS - star diagnosis system - our scanner
  • VAT- old school carbon pile battery tester
  • CGW- central gatwey- its the module that all the communication wires from all the modules connects to so they can all talk also the cgw has all the coding for what modules should be in the car
  • Xentry- its a program for the newer cars inside the sds, so the first version was HHT- hand held tester- then they came out with a laptop called DAS- diagnostic assistant system- now we are on Xentry .

hope this give you some intel into our world :)

Customer: replied 12 months ago.
Ok retread current reading with 2 different amp meters. Same results: fluctuations in current from 5.0 to 42 milliamperes. Hum. Thoughts? Pull fuses until I see the fluctuations go away?Thoughts: switch or module with a resistance issue?
Expert:  Lou P. master tech replied 12 months ago.
A module is keeping the systems awake. So you are saying to be clear from 5 amp to 42 mA?
And yes since it's consistent draw although changing numbers , start to pull fuses to see what will kill it.
Customer: replied 12 months ago.
5 milliamperes to 42 milliamperes. Not sure this enough current drain.
Expert:  Lou P. master tech replied 12 months ago.
Yeah you are correct that is not enough to draw. Although 42 is 12 over acceptable I don't think you would find the draw. This would be a first but go ahead leave the car unlocked and see what the draw stops at after 1 hour. If you have the keyless go system then make sure the key is further than 10 feet away.