W212 A207 Cab - ECO not always available

[wozzlegummich]

AFter a cold start my ECO (engine start stop) is not always available. Especially after the cars has been sitting for some time. I suspect a battery low voltage issue but which one? Front or rear?

[T-Modell]

Hi wozzle (funny names in Oz ),

imho that's normal. I have it in my W222 and especially during Covid (only short distances), the "brain" of the control units decides, that the battery is not strong enough. I do remember, that in the manual there is a chapter which lists the conditions, when the ECO is active or not (there's quite a few). Especially directly after starting the car (warming up) it might not work (too much power drainage) and I found out, that if it is very hot or very cold (aircon resp. seat heating) it doesn't switch off. Generally it's working, if the battery is in good shape and full.

Kind regards
Thomas

P. S.: What you can do, is to put your car on a good charger (CTEK) overnight until this says it's full ... then it should work, at least after a few kilometres.

[John Green]

imho that's normal.

What Thomas said. The stop start function has a bunch or parameters that have to be met before it will start to work. To do your own check, you need to either follow Thomas's idea of fully charge it overnight, or take it for a good drive, at least an hour long. If it is still not working within around 5-10 minutes the next day, maybe the battery is on the way out.

Out of the two batteries you have it is usually the main start battery that will fail first.