1.4 Amp Draw

Fred Owner/Technician Santa Barbara, California Posted   Latest  
Question
Electrical
2003 Mercedes-Benz E320 3.2L (112.949) 5-spd (722.6)—WDBUF65J13A102201
Dead Battery

This vehicle has a 1.4 Amp draw after 20min of sitting, I went to the trunk found the rear pre fuse box and removed the red wire for the drivers SAM as well as the two fuses in the interior fuse box that feed the drivers SAM, draw still remains after 10 min. I reattached those connections and removed the red wire that powers the rear SAM, same results, I then removed the red wire that comes from fuse 81 in the rear pre fuse box, the draw goes to .07 mA.

My wiring diagram shows this feeds the Interior fuse box left side of dash.

Then I went to the interior fuse box and removed 1 fuse at a time draw will go down slightly, so I pulled all the fuses from the interior fuse box draw goes to 300mA

Why does the draw go to .07mA with the red power feed wire removed from the rear pre fuse box, but will only go to 300mA when I pull all the fuses out?

This red feed wire must go somewhere else? But where? I don't think it's shorted to ground, it never blows fuse 81

Thanks for reading this post and thanks for your help 

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Andrew Technician
Commack, New York
Andrew Default
 

Hey Fred, For starts, have you ever used voltage drop for parasitic drain diagnosis? us​.​autologic​.​com/news/testing-p… Typically you won't get far pulling fuses with an electronically complicated car like that one. Before you go crazy with testing drop the driver's knee underdash panel, pull the gateway module and check for corrosion of its connector/pins. It's not

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Ronnie Owner/Technician
Raleigh, North Carolina
Ronnie Default
 

Voltage drop is a good way to go. Just as a sanity check I have seen a lot of seat control modules cause a problem but also a few E class cars. easy enough to unplug

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James Owner/Technician
Pike, Pennsylvania
James Default
 

Try disconnecting the power seat modules for the front seats that is a very common problem on your vehicle

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Andrew Technician
Commack, New York
Andrew Default
 

Yes but if you do just one there will definitely be parasitic draws related to the CAN network disruption. If you pull fuses for the pair you might get away with this but it's not an ideal method.

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James Owner/Technician
Pike, Pennsylvania
James Default
 

I've literally had over a dozen late 90s early 2000 Mercedes with seat module failures over the years, so based on the amount of draw shown we've gotten used to disconnecting the modules first as they are easily accessible. I certainly agree a good plan for searching out parasitic draws or any failure is the best method for diagnosing anything. But as with anything some things are just known

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Andrew Technician
Commack, New York
Andrew Default
 

Yes it works fine on the 203 which commonly had this issue on early production. I've seen first hand that it doesn't work on the 211.

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Glenn Owner/Technician
Houston, Texas
Glenn Default
 

Mercedes has a bulletin No.: S-B-54.10/162 issued in 2006 discussing, what they call "Quiescent Current Test Via Voltage Drop at the Fuses" very informative. IMO it's the only way to go.

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Fred Owner/Technician
Santa Barbara, California
Fred Update
 

I will be following thru on your input, there is an interesting point in AR54.10-P-1030T testing quiescent current consumption After preparing the vehicle, It does talk about pulling fuses to find the draw. Point 13.2 states to pull fuses one after another to locate defective module I thought I was on the right track do just that. I will do the voltage drop method tomorrow Thanks again

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Andrew Technician
Commack, New York
Andrew Default
 

Have a look at this attached guide. Checking if the CAN network is going to sleep and avoiding things which cause it to wake up can be very helpful. If a module loses power or is disconnected while the CAN network is awake it's very likely the CAN will not go to sleep, which could be due to the CAN wake/sleep strategy. The gateway module keeps track of the wake/sleep status of all modules on

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Terry Technician
Gillingham, United Kingdom
Terry Default
 

Hi Fred Have you carried out a short test on all the control units and if so what fault codes do you have ? i would in particular be interested in the front and rear SAM modules. i would like to gather all known information before diving into fuse removal for quiesecent drain testing. Here in the UK we have problems with the alarm signal siren causing battery drain but first off check the codes

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Michal Owner
Houston, Texas
Michal Default
 

un plug over head control panel, leave all fuses in and see what the result is

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Fred Owner/Technician
Santa Barbara, California
Fred Update
 

Here is where I'm at, the rear pre fuse box fuse #84 1.2v drop battery control module Interior fuse box fuse #21 .1v drop right rear door control #22 .2v drop RF door control # 23 .1v drop RF seat control #31 1.1 v drop Drivers Sam #41 1.2v drop for Central gateway module #42 .6v drop Drivers SAM Me- SfI the other fuses show 0 Under hood fuse box drivers SAM #64 1.3 v drop instrument…

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