Marvin-X

Hello everyone.

I am not sure if your 2014 e350 coupe needs a jump start to start. The battery is good, occasionally it goes dead, sometimes the auto start stop doesn't work, steering wheel assist disappears, 360 camera no assist line, but after driving for a while the auto start/stop will work again.

When I notice the battery is dead, I charge the battery with the charger, but to no avail, it still won't start. When I use jump start to start the car, all functions are normal. But it won't last long. I want to know if I need to replace the auxiliary battery.

I went to dealer many times to check and I couldn't find the reason.

If this is happening to your car, please let me know how you fixed it. I will try it on my car.

Thank you in advance.

pl626

What's the voltage of the battery after charging? It sounds like there's a problem with your charging system, i.e, alternator not supplying enough or battery not able to hold charge. How old is the starter battery? If it's older than 4 or 5 years, you probably should replace it.

Marvin-X

I replaced the battery with a new one 1 month ago, even though they tested it and said my original battery was good.

I think there should be no problem with the alternator because every time the battery was lack power when I drove for a while, some functions came back to normal.

I'm wondering if there is something wrong with the auxiliary battery, aging or some leakage that is preventing it from starting.

Because I know the auxiliary battery mainly powers the dashboard and electronic steering wheel boost, multimedia.

Every time there is a lack of power, the steering wheel assist disappears and the yellow auxiliary line of the 360 camera disappears.

The_Judge

This is weird! Why is the original post in Chinese?

pl626

LOL, I used the browser translate to read, but there was definitely something lost in translation.

OP - Can you take a voltmeter and measure the voltage on the battery when engine is off? Also, what's the reading when the engine is on?

Marvin-X

Sorry about that, I forgot to use English. ^-^.

My friend checked it for me a few days ago. I forget the exact number, I will check again recently.
At that time, only the values when the engine was off were checked and showed normal.


Thanks，

pl626

If this reading is below 14v when the engine is on, you most likely have an alternator issue.

Marvin-X

I'll let you konw when I got the reading.

Marvin-X

i used the OBD II to measure i got VPWR 13.59V when the engine is on. I did not use a multimeter to test. I am not sure if this obd ii measured value is reliable.

pl626

I'd still use a dedicate volt-meter to measure charging system capacity. You can always pick up a cheap multi-meter at any autoparts store or online. You don't need to have an expensive Fluke. I keep a multi-meter in each of my vehicles.

Marvin-X

hi,
I measured it with a multimeter and it was a completely normal value. When the car is completely dormant the voltage is 0.06. My car has no problems found now.

I now find that when the battery connection is taken off and reconnected, the car does not have a problem. I consulted with the mechanic and he said that maybe there is a problem with one of the modules but it will take a lot of time to find it.

cheers,

Chevota

Fyi the Eco start/stop was the first thing to go when my batt was getting low. It actually did this maybe a year before I noticed any other issues. The next issue, if I recall correctly, was the rear camera would randomly not work. Then a couple months later it started to randomly misfire at idle, then days later misfire at low rpm driving. The batt was something like 6 years old? It had lower voltage than a new one but certainly not low enough to cause issues, and should never cause issues once the eng was running, but it did. A new batt fixed it. Since the low batt can't physically cause those issues, I firmly believe the ECU simply creates the problems. The Eco start/stop fail is for a reason; they don't want people to see Mercedes dying all over town and blocking traffic so it only works if it's sure the batt is tip top. Since the car is clearly capable of checking voltage when it's off, no doubt cranking voltage too, it's not a stretch to believe they added the other issues. I'd assume it's to get you take it to the dealer so they squeeze you for $ because what other reason is there?

On my backup cam it was either a completely black screen or black with the yellow lines.
I still have the oem aux batt, which I suppose I should change too but I read it's only function was to ensure the tranny could be put in Park if the main bat was dead. Probably does other things but that's all I could find on the subject. It is odd that my aux batt is rather large (12AH), larger than most MB aux batts and clearly overkill for Park.