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sprinkles08
sprinkles08, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 22648
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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I have a 2009 c300 that I just started having issues with.

Resolved Question:

I have a 2009 c300 that I just started having issues with . Left me stranded one day , then I got it started . Seemed to be dead like the battery was shot , replaced battery for the vehicle and battery in the key . Checked all fuses in the fuse box , all seemed to be fine . I'm getting a clicking sound from the "prefuse" box when opening the door . No power to ignition , Windows won't roll up or down , remote key lock and unlock won't work . Any help would be appreciated before I spend thousands at dealer
Submitted: 1 year ago.
Category: Mercedes
Expert:  sprinkles08 replied 1 year ago.

Hello and welcome to JustAnswer!

If the vehicle is electrically dead then a power distribution, battery or cable/connection issue are likely. If it's just items that need the key to be on to operate that won't work then you may have an electronic ignition switch issue.

It appears that the battery was replaced previous to the current issue, if that's the case then the battery may be dead now. When was the battery replaced opposed to the current no start situation?

Customer: replied 1 year ago.
Battery was replaced earlier this year , I have power to radio and interior lights , when I open the door I hear the prefuse box make a loud click.
Expert:  sprinkles08 replied 1 year ago.

Have you tried a jump start?

Customer: replied 1 year ago.
I have tried to jump start , didn't seem to make a bit of a diference . I can go out and try another battery I have an optima red top o can try on it
Expert:  sprinkles08 replied 1 year ago.

If you have a second battery to try that would be great.

Customer: replied 1 year ago.
Yeah I will go do that now and let you know the outcome so we can go from there
Expert:  sprinkles08 replied 1 year ago.

Ok.

Customer: replied 1 year ago.
Ok switched battery nothing changes , just getting a single click out of the pre fuse box no power to ignition , only thing that works is radio and odometer will light up when door opens
Expert:  sprinkles08 replied 1 year ago.

Does keyless entry work?

Customer: replied 1 year ago.
No keyless entry doesn't work . I took a couple videos but won't let me send them through this site
Expert:  sprinkles08 replied 1 year ago.

Do you have a big chain parts store such as Autozone?

Customer: replied 1 year ago.
I do right up the road not even 5 minutes awy
Customer: replied 1 year ago.
Here's a list of fuses with power and without ... With power / 1,2,3,11,12,13,14,15,16,17,18,19,20,26,27,28,31,32... Without power 4,5,6,7,8,9,10,21,22,23,24,25,29,30,33,34 . This is all from main fuse box under the hood
Expert:  sprinkles08 replied 1 year ago.

I believe the problem is most likely with the electronic ignition switch but without having a full capability scan tool there isn't' a way to diagnose it properly, and a scan tool would be needed for the repair either way. It's possible that the key is the issue and while they wouldn't be able to tell anything about the transponder, an Autozone would be able to test the key fob's keyless entry output for free. If the fob wasn't transmitting then you know for sure it will need to be replaced. Again to program a replacement fob though it's going to require a dealer level scan tool.

Customer: replied 1 year ago.
With the eis failure shouldn't I still get some sort of power to the dash still and get a Error message ?
Expert:  sprinkles08 replied 1 year ago.

Not if it isn't registering that the key has been turned to the run position.

Customer: replied 1 year ago.
What do you think the clicking sound when i open the door and the power gets transferred though the junction box is .
Customer: replied 1 year ago.
I have power to all four post on the junction box when I open the door , if I close the door and wait for a couple minutes I only have power to the two bigger post
Expert:  sprinkles08 replied 1 year ago.

It's most likely an internal relay, I wouldn't be concerned with it.

Customer: replied 1 year ago.
a this point you wouldn't think it was a power issue
Expert:  sprinkles08 replied 1 year ago.

Not if the battery has been replaced with a known good one and the cables are clean and tight.

Customer: replied 1 year ago.
Yeah the battery is fine and connections are clean and tight , just find it weird the power to the key seems like it's non existent .
Expert:  sprinkles08 replied 1 year ago.

It's not weird at all. If the switch isn't working then it could just as well be unplugged.

Customer: replied 1 year ago.
The key fob is transmitting a signal I went to the auto store and checked .
Expert:  sprinkles08 replied 1 year ago.

If RKE was lost at exactly the same time the starting problem started then odds are the key is ok if it's transmitting.