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Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 29037
Experience:  Over 15 years experience as a Mercedes dealer technician
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I have a battery drain and, upon closer inspection, the

Customer Question

I have a battery drain and, upon closer inspection, the cigarette lighter is not working.
JA: Have you tested the battery with a voltmeter? And can you see if it's leaking or not?
Customer: Battery tests fine. When I turn off the car however, I hear something (I don't know what) still running.
JA: What is the model/year of your Mercedes?
Customer: 2010 e350
JA: Are you fixing your E350 yourself? What have you tried so far?
Customer: I have no Mercedes Mechanic within 50 miles, so I decided to do some troubleshooting before making the long drive to Virginia Beach. I have had the battery tested and replaced, but not much else. That is when I noticed that the cigarette lighter is not working.
JA: Anything else you want the mechanic to know before I connect you?
Customer: no, thanks ok
Submitted: 2 months ago.
Category: Mercedes
Expert:  Pete replied 2 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

On this model a dealer uses their SDS ( star diagnosis machine ) which has a program to track the component draining the battery.They plug this into your vehicle and enter a program that quickly identifies the drain.There is an older procedure I have used several times in the past before to help pinpoint it and it may or may not work on your model.It does require the use of a multi meter to locate the source of the drain.If you would like to know this procedure let me know and I can post it below.

As for the power outlet not working this is usually just a blown fuse needing replaced.Unfortunately my diagrams are not listing the fuse for this power outlet.I would check all fuses for any blown fuses needing replaced.

If you hear a component running with the key off this can be a cooling fan for a fuse panel that is stuck on needing replaced causing the drain here.This can be common.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 2 months ago.
Online sources seem to indicate that fuse 71 in the trunk fuse box is the necessary fuse for this circuit. Your sources don't have that?
Expert:  Pete replied 2 months ago.

Let me double check this

Expert:  Pete replied 2 months ago.

O.k.,fuse 73 or 71 is the power source for the front and rear power outlets ( rear if equipped).I did some more research to locate this as well.Check and see if in the rear fuse panel either of these fuses are blown.Usually this wont cause the battery drain though but I would locate and replace the blown fuse and see if the issue still continues.

If it does then the battery drain testing needs done to pinpoint and repair this drain issue.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time.Your 5 star rating is appreciated

Thanks Pete