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HomeJJames

Member
Joined
Dec 29, 2020
Messages
45
Location
Lichfield
Car
C Class 250d Convertible
Hi,

I am the proud owner of a Mercedes 2017 250d C Class Convertible.

I purchased the car on October 2020 and has 26,000 on the clock. Ever since I have had the car, the auto start stop function isn’t working. The light always stays yellow around the A in the dashboard and not changing the green. I’ve taken both long and short drives on good weather days (not to hot and not to cold) but still no change

From hear say, it could be either of the batteries but I am unsure what other battery there is other than the main batterie (or where this second battery may be).

Does anyone have any suggestions please ?

Many thanks and Happy Christmas and New Year !
 
Hi there, had this problem on others posts.
The battery has to be 100% charged for the S/S to operate. If the battery is not fully charging on your drives, unlikely this time of year what with heater, lights, wipers etc, put your battery on charge for a top up.
I don’t use my car much so put a trickle charge on the battery to keep it topped up.
Hope this helps.
 
I believe that the auxiliary battery on your car is in fact a capacitor (possibly located in the passenger footwell). If you scan the Rescue QR core on the fuel flap with your phone it should show you the location of the batteries.
 
Also, I am assuming that the car is out of the 3 years new car warranty period, but if you bought it from a trader (e.g. MB dealer or other non-private seller) then they should provide a warranty with the car. Worth pursuing if it turns-out that either battery requires replacing.
 
Hi there, had this problem on others posts.
The battery has to be 100% charged for the S/S to operate. If the battery is not fully charging on your drives, unlikely this time of year what with heater, lights, wipers etc, put your battery on charge for a top up.
I don’t use my car much so put a trickle charge on the battery to keep it topped up.
Hope this helps.
Hi,

Many thanks for the reply. Although I have not done much mileage since purchase, I have done a few longer journeys (80 miles or so) without stopping. Surely driving for 90 mins or so up the M1 would charge it sufficiently for the S/S to work. Could it be that the battery needs replacing ?
 
Yes, the car is just outside 3 years old but have a warranty from the dealers where purchased. I'm confident that there is no problem with the car but if the battery is original, then no matter how long I drive, it will never be 100% charged. I've attached QR code as requested, but haven't a clue how this helps ? Many thanks
 

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Hi,

Many thanks for the reply. Although I have not done much mileage since purchase, I have done a few longer journeys (80 miles or so) without stopping. Surely driving for 90 mins or so up the M1 would charge it sufficiently for the S/S to work. Could it be that the battery needs replacing ?
Also, I am assuming that the car is out of the 3 years new car warranty period, but if you bought it from a trader (e.g. MB dealer or other non-private seller) then they should provide a warranty with the car. Worth pursuing if it turns-out that either battery requires replacing.
 
Yes, the car is just outside 3 years old but have a warranty from the dealers where purchased. I'm confident that there is no problem with the car but if the battery is original, then no matter how long I drive, it will never be 100% charged. I've attached QR code as requested, but haven't a clue how this helps ? Many thanks

Use your mobile camera on that barcode , it takes you to a mb info card , showing the battery locations. Is your aux battery not in boot under a black plastic cover , drivers side ?
 
Use your mobile camera on that barcode , it takes you to a mb info card , showing the battery locations. Is your aux battery not in boot under a black plastic cover , drivers side ?
Yep, seems to be in the boot but I still don't know if its that which is the cause. I will speak to MB as the car is fully serviced (most recent only 1000 miles ago) and see what they say. May be battery or just a software issue - either way they should be able to help. Thanks
 
I don't understand why MB cars have so much trouble with the ECO stop/start. My ML350 hardly ever had an active stop/start but my Audi stop/start happens all the time unless I turn it off permanently (which I have).
 
It could be a problem with the battery but before doing anything else I would charge the battery with a good quality trickle charger. A good one can bring a battery back from the brink to good health, but an average one will help you work out whether there’s a fault.
 
I don't understand why MB cars have so much trouble with the ECO stop/start. My ML350 hardly ever had an active stop/start but my stop/start happens all the time unless I turn it off permanently (which I have).
Perhaps the conditions which have to be met are different. In real life I come across far more people complaining that they have to put up with stop-start than complaining that it doesn’t work 😁
 
I doubt the state of charge criteria is really 100%. A battery will reach 80 % of charge relatively quickly but the only way to get it to 100% is to have it spend a long time on a charger. A 90 minute motorway drive mostly likely wouldn't do it.

Whatever senor is used to measure the state of charge could be faulty.
 
Yep, seems to be in the boot but I still don't know if its that which is the cause. I will speak to MB as the car is fully serviced (most recent only 1000 miles ago) and see what they say. May be battery or just a software issue - either way they should be able to help. Thanks
Mines a C250d saloon so similar to yours. I hadn't considered where the 2battery might be but I'll look tomorrow. Just to say my s/s fails to work most times at present. Lots of criteria affect it include engine and outside temperatures. Long constant speed journeys don't charge it fully, shorter journeys with frequent braking are better and I find then that the indicator suddenly turns green. One of the dashboard displays shows when it's charging which is only when you are braking or coasting.
 
Our 2019 C300 (on just over 6000 miles) has the same issue - the Mercedes Me app shows the battery status as 'partially charged' at all times, even after a 200 mile trip. So either the battery is degraded or there's something wrong with the way the voltage is being measured. It's being looked at under warranty in a couple of weeks.
 
Do you have AC on all the time. That would stop it from working.
 
It could be a problem with the battery but before doing anything else I would charge the battery with a good quality trickle charger. A good one can bring a battery back from the brink to good health, but an average one will help you work out whether there’s a fault.
Hi, I have never heard of a trickle charger before but will have a look into it. My previous car was a 15 year old Fiat so this is jumping from the stone-age to the 21st Century in one go. Could you advise how trickle chargers work ? Thanks
 
Do you have AC on all the time. That would stop it from working.
Hi, no don't have A/C on, just open window if to warm. Besides, I'm to tight on my fuel consumption so I run as economical as I can :)
 
Hi, no don't have A/C on, just open window if to warm. Besides, I'm to tight on my fuel consumption so I run as economical as I can :)
You should really always have AC on, any cost savings by having it turned off are more than taken up when it needs repairing due to limited use.
 
Our 2019 C300 (on just over 6000 miles) has the same issue - the Mercedes Me app shows the battery status as 'partially charged' at all times, even after a 200 mile trip. So either the battery is degraded or there's something wrong with the way the voltage is being measured. It's being looked at under warranty in a couple of weeks.
Interesting to note....seems like a problem with batteries or a potential sensor fault ? I've just booked the car in for a diagnostic check (which MB are relieving me of £110 quid !) but hopefully this will let me know. They suggested its the auxillary battery but wont know until diagnosed.
 

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