shamrode

The car hadn't been started in a week and yet started up beautifully. After about 15 minutes of heavy traffic all at once my dash board light up red as seen in the diagram showing me the picture of a battery. I pushed the button "ok" and the red disappeared however was saved in the "service messages" section. My Bluetooth and radio LCD closed and the buttons surrounding the cd section turned off. I continued driving the car for another half hour until I returned home. I shut of the car and restarted. After 30 seconds the battery light lit up again. I have the tester seen below and the car tested as follows 1. The alternator tested ok (Diode Trio Functioning.) 2. Battery Load test was 11.3V (above 10V is good.) "Charging Test" after 10 seconds was 14.18V (between 13.5 and 15.5V is normal.) All of these readings look ok unless this is not applicable to Mercedes. I have had for the last two weeks a dash cam connected to the cigarette lighter even while the car is turned off; however, it shuts down when I turn off the engine. I was told that perhaps it is my secondary or auxiliary battery that caused this. Do I have one?
Guys my unit is stationed in the far east; dangerous to be stranded out. Please help

INS1GNIA

You have a battery under the hood and one in the trunk, next to the spare tire.

ZephyrAMG

I keep telling people that you gotta change out your battery every 4-6 years regardless. Just got to. If its premature power loss you gotta look at your alternator...

shamrode

Hold on; I have under the hood??!! Where? The one in the trunk I changed 5 months ago. I don't see anything anywhere saying that the 2009 has this aux battery.

ZephyrAMG

A battery under hood and one in the trunk, right side or passengers side, under the floor board.

The one under hood is on the passenger side also if I remember correctly. It has a red terminal top.

INS1GNIA

This almost sounds like the start of a joke lol. Though the battery is kinda concealed.

Diabolis

WTF are you guys on about?? There is a boost terminal under the hood, but there is only one battery in the trunk. Where exactly is this concealed battery, please?

shamrode

This what you have in red from the picture. It's a fuse box.

Jasonoff

From what I remember, when I was looking last year, most if not all of the battery searchers for each manufacture show an auxiliary battery that we do NOT have.

Exide search example.

JordanSpaceJam

I had this happen on my 2012 Coupe and it turned out to be the voltage regulator. Ended up putting a new battery in too while we were at it and now its fine.

INS1GNIA

Diabolis

Guys - what you've got there is just the boost (jump) terminal. Up and to the left (under the large cover) is the cabin air and below that the ECU. There is no aux battery.

Agree that the symptoms point towards an alternator or voltage regulator issues.

TurboRush

+1

shamrode

How can one determine whether it is voltage regulator or the alternator? My tests from my first post showed all was good. Could my dash cam that is connected to the lighter cause issues?

INS1GNIA

Makes sense. My apologies shamrode.

ZephyrAMG

huh....interesting. Always thought it was a small battery due to the red terminal cover. My bad. Thanks experts.

CarHopper

Nope, but a good thing to know in case you need a jump and have a few bodies in the trunk you'd like to remain in there.

realjones88

If you are doing a lot of short distance driving or not driving the car for long periods I'd consider hooking the car up to a battery tender or trickle charger. I had one of those silly progressive data things on my car for a couple of days then didn't drive the car for a week. This thing has no shutoff and ate my battery up (down to like 9v). The Batteryminder brought it back from the dead. This may be what's happening with your dash cam even though you think it's shutting off.

shamrode

If I go to a Mercedes dealership and they connect the car to their scanner can it tell me what caused the error even though it is in the past? Does the car's ecu retain error history? Also how does one determine whether it is the voltage regulator or the alternator that is the culprit?

Diabolis

Shamrode - unless the dashcam connector in the lighter socket is faulty and shorting out, the issue could be anything from a bad ground connection (although unlikely) to a problem with the alternator, voltage regulator or the battery itself.

Specific error codes as to what went wrong will be stored in the ECU - do you have an OBD II code reader (scanner) by any chance?

Diabolis

Yes. The codes will indicate where the problem is.

shamrode

Thanks for the reply. I just bought an obd2 connector made by Elm (elm327.) I connected it to the OBD port and scanned for error codes and nothing came up. The question is if the car is no longer showing the red battery light if the elm scanner will pick something up in the ECU history. It did give me a po365 fault code. Any clue what the code is?

TurboRush

Looks like P0365 Camshaft Position Sensor 'B' Circuit Bank 1

AA717driver

Good to know...especially if you live and "work" in NY.

My 911 had remote posts for charging in the engine bay.

TC

shamrode

Dude, in English please.