[craggyislander]

My car hasn’t shown fully charged since the pandemic began. Well, that’s not quite true, it was fully charged for 2 weeks after its 1st service and I think they had to charge it in order to update to FU3. Other than that it always says partially charged but I don’t receive any warnings. I have assumed that my once a week drive of 28 miles isn’t enough - mileage/time/correct type of drive - to keep the battery at full charge. The only driving I do on top of this is the occasional down the road trip to take my parents provisions which likely does more harm than good. FYI, my stop/start is always automatically off too, presumably to ensure no overtaxing of the battery. I don’t think there’s a problem with the battery, just a lack of reasonable use. I won’t worry unless the warnings start.

Very helpful thanks 😊

 

[Greenjacket]

I took my car in to the dealers last week for the A/C recall, while there ,they replaced the A/C sensor. I also had the problem of abs light on, along with lane assist, brake assist, esp and stop start not working.
As per the COVID rules, I couldn’t have a curtesy car or wait for the work to be done, resulting in me walking the streets for four hours!
collected the car, all ok, until yesterday, lights are all back on.
I was near Halfords, who kindly done a quick battery check, and said it shows an error!
Took the car home, recharged fully, green light on ctek charger. Took the car for a forty five minute drive, all good for a short while, everything working, but now all the warning lights are back on!
Considering, that the ctek charger fully charged the battery after a few hours, it went through all the stages, what do you guys think? Auxiliary battery perhaps?
I’m taking it back to the dealers Friday ( 30 mile round trip again) !

 

[Greenjacket]

Had my dealership check my battery on several occasions and told ok!
However, when I check with a volt meter after a full charge with my ctek charger after standing all night, it shows 11.8.
With engine on I get 14.8.
Occasionally, when starting the car, I have had numerous dash lights appear, abs, lane assist etc, stay on, but no engine management light.
when I drive the car for about five minutes, the lights and messages go out.
It’s been suggested that if the battery voltage drops below a certain point the ecu can trigger such lights temporarily, until battery receives required charge above 11.8. Messages that were showing are then extinguished, None are stored.
Any forum members have any thoughts?

 

[Macgd016]

However, when I check with a volt meter after a full charge with my ctek charger after standing all night, it shows 11.8.

Personally I would say that your battery is not holding its charge which could mean the battery is faulty or something is causing a load when the car is switched off.

It is difficult to get a meaningful voltage reading on these cars even with a volt meter because some of the electronics are active even when the car is switched off, the correct way would be to disconnect the battery and then charge it with your ctek, leave it for several hours to stabilise before taking a reading, you would expect to see a voltage above 12.6v. If it is less than this you would suspect a faulty battery.

Another way of doing this without disconnecting the battery, its less accurate but easier, is to open the bonnet and lock the car. Leave the car like this don't unlock it, charge the battery, leave it a few hours hours and then take a reading if you are still seeing 11.8v I would say the battery is faulty or something on the car is switched on that shouldn't be.

I did some testing over several weeks in the first lockdown when I wasn't using the car at all. I did the tests as above and found I was getting a voltage drop of approx 0.03v per day which meant my battery was dropping from 12.7v to its critical level of 11.8v in about 28 days, not a major issue in normal daily use but not great if the car is laid up. My dealer did a full diagnostic on the car and found that one of the can bus was switching on too frequently so reset the module and replaced the battery and I've had no problems since 🤞 .

 

[Greenjacket]

Thanks Mac. If I lock the car, wouldn't the alarm still be active?

 

[Macgd016]

Thanks Mac. If I lock the car, wouldn't the alarm still be active?

Yes it will but there doesn't seem to be a sensor on the bonnet so the alarm shouldn't go off unless you really shake the car. I did this over several weeks just leaving the bonnet on the catch, opened it to test the battery & lowered it again afterwards.

And yes the alarm system will put a load on the battery but this method is more convenient than disconnecting the battery, so although not perfect I think it is the next best solution. The reason for locking the car is that I think this is the best way to minimise the electrical circuits that are active but even after locking the car it take half an hour or so before everything switches off. You can see this with a voltmeter but you can also hear it if you stand by the car after locking it, you will hear all sorts of clicks and other sounds as things power down.

 

[Belongabob]

I recently had a few minor issues with mine, POIs not always showing, sometimes losing 'Home', etc. A week before the car was due to go in for the update (FU3) the start/stop packed up. The car is still under warranty.

My dealer (Sandown Mercedes in Newbury, Berks) did everything I asked for without question and also replaced the battery as it was likely to be the culprit.

So far, so good... but I must say I'm impressed with Sandown in Newbury, they have only just taken over the franchise this February and seem to be just as professional as the previous owner, Sytner.

 

[Greenjacket]

I recently had a few minor issues with mine, POIs not always showing, sometimes losing 'Home', etc. A week before the car was due to go in for the update (FU3) the start/stop packed up. The car is still under warranty.

My dealer (Sandown Mercedes in Newbury, Berks) did everything I asked for without question and also replaced the battery as it was likely to be the culprit.

So far, so good... but I must say I'm impressed with Sandown in Newbury, they have only just taken over the franchise this February and seem to be just as professional as the previous owner, Sytner.

I finally sorted out my problem with the car. l purchased a new battery out of my own pocket £200.00. Although less than 4000 miles and 18 months old.
Fed up with Mercedes dealership telling me it was ok.
Had it tested by two other outlets, and told it was faulty
Car now running perfect,. STUFF Mercedes!

 

[Macgd016]

I finally sorted out my problem with the car. l purchased a new battery out of my own pocket £200.00. Although less than 4000 miles and 18 months old.
Fed up with Mercedes dealership telling me it was ok.
Had it tested by two other outlets, and told it was faulty
Car now running perfect,. STUFF Mercedes!

Well I'm glad you have it sorted but that is shocking service, it might be worth phoning MB CS to complain

 

[Greenjacket]

Hi Mac,
I initially done what you suggested, which helped Helped greatly.
It was just my sheer frustration, with numerous trips back and forth to the dealers. Forty mile round trip each time.
I’m beginning to enjoy driving the car now, no abs, lane assist, esp lights etc, appearing.
It was obvious, that these systems like their proper voltage. Although my ctek charger indicated that my battery would hold a charge, after a few days the voltage would drop, and the dreaded warning lights would appear. Mercedes answer was to give the battery a quick boost, and send me on my way!
The old battery, showed that it was three years old btw!