SL350 ECO stop start problem

goodoldfred

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The ECO stop/start function on my 2 years old SL350 seems to work on a haphazard basis. Some days it comes on within a mile but on others I can drive 5 or 6 miles and I have even driven as much as 15 before it comes on. Even then it often switches off and on again without warning. I know several parameters have to be met before it will work (temperature/oil pressure/battery charge etc.) and it seems to activate more promptly after it's been run for 2 or 3 miles or so and then parked up for a little while. The dealership staff were baffled and replaced the battery which improved the situation for a couple of weeks or so but now it's as bad as ever and I want to make sure it can be fixed whilst still under warranty.
 

television

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Hello and welcome, not sure that anyone can offer much advice on this as not a common thing on here, the only link that I can see is the battery charge level, if it was OK when the new battery was fitted, could it be that the charge on the battery is not holding up. The stop start is out of action when the battery is low.
 

tode

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The ECO function will not activate if the interior (cabin) temp. is too high or too low - try adjusting your temperature setting to the actual temp. to see if this is the cause (it takes a minute or so to react).
 

Cole@MBS

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We have seen a couple of these now, its simple with star to see whats not up to spec, star tells you while driving what good and whats not, i believe the 3 we have seen have all been batterys but the op has had that changed......
 

television

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Thats the way I read the post Cole, so if battery low, this function must turn off.

I also see that the batteries in some makes have to be coded to the car.
 

Cole@MBS

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One stipulation that made me giggle was (is driver present?)........
 
OP
G

goodoldfred

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Thanks everyone. Low battery charge seemed to be the opinion of the service people but no obvious reason why the charge would be lower than what was required. I've given it a long run to make sure the battery will be fully charged but it doesn't make any difference. When they put a new battery in they said it might not work when the aircon/climate control was on ! Really ? It doesn't say that in the manual ! Again I've tried that but to no avail. It will be the first thing I ask them to check out at the second service.
 
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geraldrobins

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My stop start still baffles me. today it came on after about 2 miles, but often after 30 miles of motorway going to work the stop start doesn't activate. Often if I restart the engine the stop start then works as expected. Ive made mental notes but have no idea why it is inconsistent.
 

daveenty

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This is for an E Class, and from a US manual which I acquired, though the same conditions should apply on yours.

The ECO start/stop function is operational and the ECO symbol is displayed in green in the multifunction display, if:

The indicator lamp in the ECO button is lit green

The vehicle is stationary.

The outside temperature is within the comfort range

The engine is at normal operating temperature.

The set temperature for the vehicle interior has been reached.

The battery is sufficiently charged.

The system detects that the windshield is not fogged up when the air-conditioning system is switched on.

The hood is closed.

The driver's door is closed and the driver's seat belt is fastened.

If conditions for automatic engine switch-off have not been fulfilled, the ECO symbol will be shown in yellow.


Now, I've checked all these conditions several times on mine, usually on the same run, and come to the conclusion that there are three distinct possibilities which cause it to decide not to always work: -

As the first one involves witchcraft we could probably discount that. I'm also not convinced about the second one which involves lunar phases and the positioning of the moon, so this would narrow it down to battery condition, probably combined with ambient temperatures. In other words, if the battery has had to work a little harder on an initial cold start due to outside temperatures being lower than normal, it will take longer to charge thereby allowing it to enable the system.

I have found that the easiest way to deal with it is just to switch it off, which I can do by selecting S Mode. This works for me but, unfortunately, it defaults to C Mode on every start, so I still have to think about it everytime I restart it when fuelling or whatever. Mine is quite loud on start up so I don't particularly want the stop/start function enabled in town as it tends to alarm people who are stood near the back of it, though can appreciate that it would be beneficial on a standard car, not least for the fact that it's designed to operate to save fuel.
 

television

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Your car a little loud on start up Dave, That cannot be right :rolleyes::rolleyes:
 


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