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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4602
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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My battery is dead and I do not have the silver valet part

Customer Question

my battery is dead and I do not have the silver valet part of the key fob. long story on that one. also was able to get to trunk via the back seat, and I did find the green button that you are suppose to be able to press down to release the trunk hood, pressed it with a lot of pressure as well, and nothing happens
Any way to use a separate battery to charge the car enough so that electrical works so that I can get into trunk and replace battery?
Submitted: 1 year ago.
Category: Mercedes
Expert:  Lou P. master tech replied 1 year ago.

Hello, yes you can use another battery with jumper cables to get power to the car to pop the trunk. the green button is electrical so it will not pop the trunk if the battery is dead.

Customer: replied 1 year ago.
Great. Since I cannot get into the trunk where one would normally connect a new battery to the terminals, where do I connect the new battery? How do I connect it? I have jumper cables but do not know where I can attach them?
Expert:  Lou P. master tech replied 1 year ago.

well you said you got into the trunk through the back seat, can you not access the battery? the battery is under the panel, i know you will not have much room but it is doable.

Customer: replied 1 year ago.
There is no way to squeeze through. The only section that comes out is the middle section, which is not very wide at all. Also there are metal bars which makes it even more narrow.
Expert:  Lou P. master tech replied 1 year ago.

oh gotcha, i was wondering how you got back there lol, so do you have the fold down seat option?can you reach the handles at the top of the rear deck if you have that option? if not the next option is to pull up the passenger side carpet in the front and jump the battery at the floor prefuse box.

Customer: replied 1 year ago.
Also the battery is located next to the spare tire. In order to get to that, you have to unscrew the plastic part, remove it, and then remove the large section that was covering the battery and spare tire.
Customer: replied 1 year ago.
unfortunately, do not have fold down seat options
Expert:  Lou P. master tech replied 1 year ago.

i understand trust me, i have never had to do it this way, i know it is very hard , so i am on the same page with your. you have to access the fuse box under the floor on the passenger side then., i have to leave for a bit, i will check back as soon as i can.

Customer: replied 1 year ago.
Jump the battery at the prefuse box? I did locate the small auxiliary battery under the hood, and tried to jump from there, but it did not work. I am not aware of what a prefuse box is?
Expert:  Lou P. master tech replied 1 year ago.

access that fuse box in the picture, use the positive cable on the big black cable and negative on the body chassis. only use that to pop the trunk or you will blow fuses if you try and start it.

Customer: replied 1 year ago.
okay. I will check for the fuse box underneath the floor. my question though is after I get to the fuse box underneath the floor, what do I do to get power to it? Attach the jumper cables to what? Are there any terminals? etc. Please explain.
Expert:  Lou P. master tech replied 1 year ago.

my last text should explain

Customer: replied 1 year ago.
Got it! I thought it would look like an electrical fuse box with little fuses in it.
Expert:  Lou P. master tech replied 1 year ago.

ok so you got it jumped?

Customer: replied 1 year ago.
my cables are in the trunk! so my I finally got my neighbor to come over and help. He works on cars. we got to the fuse box, but in the pic you attached, on the top leading in, there are four wires. Red black green yellow. On my fuse box, it only has the last two wires, the red and yellow. No red wire leading in? My friend tested the green and yellow to see if either was "hot" but he gets very little reading back.
Customer: replied 1 year ago.
sorry it took so long. FYI - I do want you to know that once we figure this out, I will make sure and pay the fee, as well as complete the rating for you.
Expert:  Lou P. master tech replied 1 year ago.

OK SO on the fuse box we want the big wire that is bolted to the top of the box, that is the power wire from the batter positive cable.