Stop Start question

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Jimmcb

Active Member
Joined
May 5, 2023
Messages
75
Location
Scotland
Car
E53 amg 4matic
Today on a nice drive in 2017 GLS 350d to Perthshire Scotland from Edinburgh area (circa55 miles) I noticed SS light on dash was orange ie not functioning.

I had air con fan on at low speed and medium temp.

However, as soon as I switched A/C off, SS light went green on dash display and was available and functioning.

Anyone care to offer thoughts please?

The battery OUGHT to have had sufficient charge so I’m guessing it wasn’t the battery charge levels, but I’m happy to be educated.

Jim
 
Last edited:
The battery might be starting to show it's age, and no longer hold its charge like it used to.

OR

The car is simply programmed to disable Start/Stop when the aircon is switched on and the temperature inside the cabin is still higher than desired - the obvious issue is that if the engine isn't running, the aircon compressor won't be working either.
 
You probably have two batteries, or one battery plus a capacitor?
Both need to be 100% for it to work.
I've had both my battery and capacitor replaced and stop start will work regardless of air con or any other consumables. (unless its -5c or +28c where heating/cooling will take priority)
So I would say it's 100% battery charge related.
 
Thanks guys. In truth that’s what I thought (feared) but I’m new to MB so happy to gain views of yourselves. Much obliged.

Jim
 
As markjay says, it could be that the car simply turns off the start/stop depending on the setting of the aircon and how that compares to the car's internal temperature. However, I live in the area that you were driving today, and when I was out and about today the outside temperature was never above 4°C, so unless you like your car decidedly chilly while you are driving, it seems unlikely the aircon was having to work too much.
If your battery is the original one I'd be inclined to suspect it might be weakening. I changed my battery last year and still find that in cold weather the stop/start is reluctant to activate in winter. In summer it goes green pretty much straight away.
 
As markjay says, it could be that the car simply turns off the start/stop depending on the setting of the aircon and how that compares to the car's internal temperature. However, I live in the area that you were driving today, and when I was out and about today the outside temperature was never above 4°C, so unless you like your car decidedly chilly while you are driving, it seems unlikely the aircon was having to work too much.
If your battery is the original one I'd be inclined to suspect it might be weakening. I changed my battery last year and still find that in cold weather the stop/start is reluctant to activate in winter. In summer it goes green pretty much straight away.
Thank you. I’m just over the bridge west side Edinburgh.

Do you use MB Halbeath?
 
The battery might be starting to show it's age, and no longer hold its charge like it used to.

OR

The car is simply programmed to disable Start/Stop when the aircon is switched on and the temperature inside the cabin is still higher than desired - the obvious issue is that if the engine isn't running, the aircon compressor won't be working either.
It'll be the latter.

In recent years since the intro of real world driving emissions (RDE) and post dieselgate they have to make sure the declared emissions are easily achievable. So they can't be seen to deactivating such emission saving features so readily any more.

Your car prob is before they cleaned up their act.

Battery state of charge doesn't change that quick just because you turn off a consumer.
 
It needs to meet the following conditions depending onthe model

The ECO start /stop function is operational and the 1707945881636.pngECO symbol is displayed on the multifunction display if:
  • the indicator lamp in the ECO button is lit green
  • the outside temperature is within the range that is suitable for the system
  • the engine is at normal operating temperature
  • the set temperature for the vehicle interior has been reached
  • the battery is sufficiently charged
  • the system does not detect moisture on the windscreen when the air-conditioning system is switched on
  • the bonnet is closed
  • the driver's door is closed and the driver's seat belt is fastened
If all conditions for automatic engine switch-off are not fulfilled, the 1707945881722.png ECO symbol is shown.
 
  • the set temperature for the vehicle interior has been reached
  • the battery is sufficiently charged

It will be one of these two conditions not met, then....
 
I had this symptom on mine when the small battery in the boot was knackered.
New battery fitted and problem solved.
 
Thank you. I’m just over the bridge west side Edinburgh.

Do you use MB Halbeath?

No, haven't used them, didn't even know there was a dealer there until i noticed it fairly recently as I drove past. I live in NE Fife, nearest dealer is Dundee. Used them for a number of years, with mixed results, while I had MB service plans. Now use an independent as far as possible. The place I use is not a Mercedes specialist but I haven't yet come across anything they can't deal with.
 
Your car is doing you a favour and you don't realise it. SS is a waste of time and detrimental to engine components, starters/ring/ gear timing chains I could go on. You'll probably save an egg cup of fuel on your journey but increase engine wear. The first thing I do after starting the engine is to turn the SS off. I don't doubt many will disagree. It was designed by the manufacturers of all makes not just Merc's to try to convince Joe public they would be saving money by saving petrol, think back to what VW did with their emission test program.
Check out Yutube or visit other forums. The general synopsise is turn it off or disable it.
Can of worms duly opened. :)
 
Your car is doing you a favour and you don't realise it. SS is a waste of time and detrimental to engine components, starters/ring/ gear timing chains I could go on. You'll probably save an egg cup of fuel on your journey but increase engine wear. The first thing I do after starting the engine is to turn the SS off. I don't doubt many will disagree. It was designed by the manufacturers of all makes not just Merc's to try to convince Joe public they would be saving money by saving petrol, think back to what VW did with their emission test program.
Check out Yutube or visit other forums. The general synopsise is turn it off or disable it.
Can of worms duly opened. :)
I agree with everything you say, but, although I turn it off, I sometimes leave it on long enough to see how long it takes to turn green and use it as an indication of how good my batteries are.
To me it's a battery condition gauge, not a stop/start device.
 
Your car is doing you a favour and you don't realise it. SS is a waste of time and detrimental to engine components, starters/ring/ gear timing chains I could go on. You'll probably save an egg cup of fuel on your journey but increase engine wear. The first thing I do after starting the engine is to turn the SS off. I don't doubt many will disagree. It was designed by the manufacturers of all makes not just Merc's to try to convince Joe public they would be saving money by saving petrol, think back to what VW did with their emission test program.
Check out Yutube or visit other forums. The general synopsise is turn it off or disable it.
Can of worms duly opened. :)
You know you're talking absolute nonsense with that entire paragraph right? What you've said simply isn't true, if it were I would have had huge bills to pay out for worn out bits on the 5 cars i've owned in the past 11 years that have all had SS tech on them - which hasn't happened, how weird......
 
You know you're talking absolute nonsense with that entire paragraph right? What you've said simply isn't true, if it were I would have had huge bills to pay out for worn out bits on the 5 cars i've owned in the past 11 years that have all had SS tech on them - which hasn't happened, how weird......

The battery and starter motor on cars equipped on Start/Stop are reinforced to meet the additional wear. Keep in mind that on a Start/Stop car, the starter will be operating around 30 times more on average than on a non-Stop/Start car. Other modifications include electric pump to maintain the hydraulic pressure in the automatic transmission when the engine is switched off.

However, this needs to be taken in context. If you always turn off Start/Stop, then the battery and starter motor will last longer, however for most motorist this simply means that somewhere down the line a future owner will need to replace it. The service life of a starter motor is very long as it is, with most scrapped cars still having the original starter motor fitted.

The bottom line is that both views are correct, yes Stop/Start does cause additional wear, but in all probability it will not be noticeable by the owner.
 

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