Another start-stop question

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I’m in a similar position. Stop Start on my 2016 W205 hasn’t worked for a couple months despite doing a round trip of 120 miles twice a week and occasionally putting it on a CTECH charger. On those trips it might suddenly work for 10mins and then stop working again. A multi-meter (I know that’s not under load) showed 12.3 volts so I took it to a local battery specialist who tested with a Bosch tester which indicated 12.33 volts and gave it a clean bill of health. Mercedes Me app also says it’s fully charged. I think it’s right on the edge between good/bad especially as I understand a good battery should read something like 12.6/12.7.
I phoned the local dealer first thing today, needless to say I’m still waiting for them to call back.
- Sorry W205
 
Last edited:
fourwheels said:
.................
I phoned the local dealer first thing today, needless to say I’m still waiting for them to call back.
- Sorry W205
Click to expand...
Relax......They will call you back but, at a really inconvenient time.;)
 
BTB 500 said:
I don't have a CTEK, but I do have a NOCO Genius which is very similar ... side-by-side comparison here:

carbatterygeek.co.uk

NOCO Genius 5 UK vs. CTEK MXS5.0 - Car Battery Geek

The 2 behemoths of the car battery charger world: NOCO Genius 5 UK vs. CTEK MXS5.0, which is the best? We go all in for this comparison!
carbatterygeek.co.uk carbatterygeek.co.uk

I've tried to use that a couple of times to repair over-discharged deep cycle / leisure batteries without any success (it has a specific 'force mode' that will put an initial charge into even a completely flat battery, which many smart chargers refuse to do). But I'm sure others will have had more luck. That aside it's a great little charger and I use it to periodically maintain the various spare lead/acid batteries I have. My AccuMate is an older & simpler design that's mainly intended for permanent connection (long-term maintenance). That works well on the SL, which is only used in good weather (the battery in that is 18 years old now). As an aside both chargers come with wall-mount brackets, which I like personally.
Click to expand...
I have the CTEK 7ah unit (MXS7) that I purchased in about 2008 and it has been a real workhorse.
 
12.33v is not a sign of a good battery, it will start your car but it isn't good enough for stop/start to function
 
Muckypaps said:
12.33v is not a sign of a good battery, it will start your car but it isn't good enough for stop/start to function
Click to expand...
Quite agree but the guy gave me the Bosch ticket which said Tested - Good and I didn’t argue with him.
Think I prefer buying from Mercedes still waiting for them to phone me back so I can book it in.

Thanks for the advice.
 
Like so...

20210228_142945.jpg


And strangely it still starts the car no problem 11 months after this reading .

Can't say about Stop Strain as I binned it years ago .

Quite simply Stop Start won't save money , it will cost you money .
 
My W205's start stop stopped working a couple of years ago. I don't know when it stopped as I always turned it off before starting each journey. It not working saved me from dissabling every day, so never paid any more attention to it. The car always started without a problem no matter the outside temperature. It was only when I came to sell it that I thought I'd look into it. Very occasionally after a long journey (600 miles to Aberdeen from the SW for example!) the light would go green and it would work a couple of times.

I believe that a new capacitor should solve the problem. They're around £25-£30 ish from various places (including Amazon!). There's a video on YouTube (easy to find) that shows how it's replaced and it seems like an easy 1/2 hour job. It's mounted in the footwell (passenger in the US, so maybe drivers in the UK?). Maybe worth a bit more resarch and perhaps a punt at £25.

Here's a link:
blog.fcpeuro.com

How To Replace A Mercedes-Benz W205 Auxiliary Battery

The auxiliary battery in the Mercedes-Benz W205 isn't a battery. Instead, it's a small capacitor used to store energy that helps with the stop/start function and switches the transmission into park when the battery dies. Regardless of what it is, the battery's performance is critical to those key...
blog.fcpeuro.com

I've just bought a 2016 GLE 350d who's start stop also doesn't work. It's a niggle that it doesn't work just because its there and it should .. however, it's a PITA, so happy for it to not work :)
 
Had the same with my w205, only once of twice the light went green, i took it back where i bought it from they put a tester on it and said its not a good as it could be, (everything else worked perfectly) they replaced the battery Varta amg, worked straight away and always worked since. Now i get in and switch it off but i know everything is ok. :thumb: If you can get them to change the main battery all the better for you rather than messing around with chargers.
Have fun with the car and pop up a picture we love a merc :).
 
Ok an update on my troubles.
The battery test on Dec30th indicated 12.33v and Battery Good, except I knew it wasn’t.
Today Mercedes Dealer insisted on full diagnostic at £190 + battery cost if faulty.
Local Indy said much the same but £80 plus battery.
Halfords, free test but with fitting charge comes to something like £185 total.
So I went to my favourite local tyre/battery place (I do know them personally). Test on a Bosch tester clearly stated Replace Battery. I went through test figures with them but not important now.
Replacement Bosch battery with 5 year warranty £220 total and I have a happy car again.
No complaint with Mercedes, they are what they are, but we do have to watch the pennies.
Thank you to all those that offered advice.
 
fourwheels said:
Ok an update on my troubles.
The battery test on Dec30th indicated 12.33v and Battery Good, except I knew it wasn’t.
Today Mercedes Dealer insisted on full diagnostic at £190 + battery cost if faulty.
Local Indy said much the same but £80 plus battery.
Halfords, free test but with fitting charge comes to something like £185 total.
So I went to my favourite local tyre/battery place (I do know them personally). Test on a Bosch tester clearly stated Replace Battery. I went through test figures with them but not important now.
Replacement Bosch battery with 5 year warranty £220 total and I have a happy car again.
No complaint with Mercedes, they are what they are, but we do have to watch the pennies.
Thank you to all those that offered advice.
Click to expand...


What battery type ?
 
BTB 500 said:
Yep it will need a new battery.

On our C Class the Mercedes Me phone app gives the battery status under 'service'. This always showed 'partially charged' when we got the car, even after a long motorway run. Everything worked fine apart from the stop/start - this was fixed by a new main battery (under warranty), and the phone app has shown 'fully charged' ever since.
Click to expand...
Do you know what the warranty period on the battery is by any chance?
 
devnull10 said:
Do you know what the warranty period on the battery is by any chance?
Click to expand...

On a new car it would be covered by the normal 3 year warranty, and replacement batteries fitted by MB also have a 3 year warranty. Not 100% sure whether the battery is still covered on 'Approved Used' cars from MB - it certainly used to be.
 
MikeInWimbledon said:
It's probably a low battery charge AND the dealer should fix it.

BUT please don't jump into replacing the battery "because the charge is low."

The five year old battery is "probably" low because the thing has been left unattended for months, and/or has only done short runs in your ownership.

A few hours on a battery charger, or preferably a proper battery conditioner, like a CTEK, would clear such a problem. A car enthusiast friend or neighbour will probably have one.

I labour the point because although the dealer may take the car in and "fix" the problem - possibly by driving the car fifty miles and so charging the car up - such a fix would only be temporary.

.
Click to expand...
Hi Mike,

Thanks for the advice, seems to have done the trick, u may have saved me a few job, hope it’s a long term solution.
 
Hi all - I was the OP - thanks for the all the messages, and sorry I did not get back in sooner. I didn't get any emails about replies.

It's a Cazoo car which despite reservations buying online I feel I got an absolutely amazing deal, saving 2 or 3 grand over a Mercedes used dealer.

Cazoo has a 90 day warranty and they have offered to fix whatever is causing the S/S but the garage who will do the work is not that convenient to get to. Not an unreasonable distance, just a pain in the bs really and lost work time needs factoring in.

As the car is perfect in every other way (apart from the Ambient Lighting going out if the back door is opened - I believe there is a software fix for that?) - I've decided to not bother getting the S/S looked at.

I suppose the only thing bugging me is it might mean the battery is poor, however everything else in the car works fine and there is no battery warning light or anything.

Just out of interest, if this were the battery, what am I looking at in terms of £££ for a new one (not main dealer prices).

Thanks again to all who replied.
 
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