W204 C180 - ECO stop start function

[Sharpey]

When engine is warm enough, and the ECO function amber ECO light on the display should turn green; it switches off completely and light on the switch goes out as if it is disabled. It has been a bit inconsitent in switching to green ECO should come since a new water pump was fitted.

 

[markjay]

Welcome.

The most common reason (though obviously not the only one) for the ECO light to remain amber and not turning green, is a partially-discharged or weak battery. This could be the main starter battery, the auxiliary battery, or both.

Check the battery voltage first thing in the morning before starting the engine, a healthy battery should show upward of 12.4v after standing overnight.

Then try to fully charge the battery, either by taking the car for a long drive, or by using a trickle charge e.g. CTEK.

If the light still switches off after fully charging the battery, you'll need a code reader (ideally STAR, but iCarsoft or Carly will also do) to check why the Start/Stop function is disabled. One other common reason is a failed brake servo vacuum sensor.

 

[molgrips]

Yep - the battery needs to be tip-top for start/stop to work. My battery was working perfectly well starting the car, even in the winter, but when tested it reported only 450A instead of 850A. So I changed it to be on the safe side and with the arrival of warmer weather it works most of the time now. I think the only reason the green ECO goes off is when it's doing a DPF regen. In winter, it also stays off when it's trying to warm the cabin, so if you find yourself with the engine running at lights for a while you can try temporarily turning the heating off.