novic350

2013 C350 4matic, 63k kms

The ECO function is no longer working. The dash indicator show yellow, but does not go green. It was working fine up until a month ago. Battery voltages showing 12.4 V at rest, 13.5+ when running. Web search points to battery condition as a likely cause, however I don’t want to go through that expense yet, as the battery is showing strong. No CEL, and no warnings.

Any suggestions on what else to check?

Odd Piggy

I’m not certain about the C Class (W204) but the GLK (X204) had an auxiliary battery to run the transmission oil pump during ECO stop. When it went bad, the ECO function would stop working.

JettaRed

iTrader: (1)

My 2014 C350 “suffers” the same ailment. Many consider it a blessing when it doesn’t work and others will pay hundreds of dollars to have it disabled. It’s a feature that is simply a gimmick to save very little gas at the expense of added wear.

novic350

A mentioned, the main battery reads 12.7V at rear and high 13s when running. The auxiliary battery in the trunk reads 12.5 at rest, and 12.76 when running, measured at the terminals. There is some sort of electrical component connect to that battery, and the leads from that read o.5V at rest, and just over 2V when running - not sure what voltage is supposed to be at this location, does anyone know? Any suggestions please?

JettaRed

iTrader: (1)

There are a bunch of conditions that need to be met for the start/stop to work, such as engine temperature, air temperature, battery levels, run-time, etc. Also, make sure your 12v accessory outlet (i.e., cigarette lighter outlet) works. I once had a blown fuse that kept the start/stop from working. The fuse is in the trunk.

Nitro350

Mine has stopped working as well & I'm fine with that.