Electrical Issues with CLS55 AMG

[RetiredSlider]

Howdy All,
Sorry that one of my first posts is asking for advice but I wondered if anybody could shed some light on the issue's i'm finding.

The Problem:
I'm occasionally getting the Convenience Functions Unavailable message on the dash. It doesn't happen often, just when the car has been left for a period of time or if the car has been started and stopped a couple of times in quick succession. The fault quickly goes away afterwards when driven for a few miles.

If pressed, both the AC and the Ventilated seats will flash, then the lights will go out and not activate. The AC can be pressed again (and still fail) but the ventilated seats fail permanently and can't be re-pressed until the vehicle is switched off and on again.

I have only recently got the car, the previous owner said he has replaced both the aux and the main battery. I have checked the running voltage on both, Aux is 12.5v and main is 13.7. I know that voltage is no indication of battery condition :-(

I have done heaps of reading on people with similar problems on this forum and the US one. I can't help but wonder if that as he was selling the car, whether he just bunged in a wrong spec battery which is not got the grunt to run everything correctly, but that doesn't seem to make a lot of sense as i would have through the alternator would provide the bulk of what the vehicle needs when running.

The car isn't down in power, everything else works perfectly and it drives fine. I don't have an engine check light or anything.

Does anybody have any thoughts or experience on this?

EDIT:
In the interest of completeness, this is the battery in the car.


Many Thanks

Chris

 

[andy27168]

Hi,
If like you say both the batteries have been replaced with the correct items then I suspect your battery control module has failed or failing. Though you do need to eliminate that the batteries haven't just got low because of the cold weather and short journeys etc.

 

[carlls]

had the same problem with my cls it was the battery in the boot that was the prob
had a new battery fitted now is fine

 

[Alps]

double check the aux battery and the date stamp, this will confirm it has been replaced or not, I suspect its the main battery, but cold weather doesn't help.

since I replaced both batteries I don't get the message anymore, before that I thought it was normal!

my main battery needed replacing after 4 years!

 

[whitenemesis]

What you describe isn't a fault, more a response to lack of use and so the battery not getting sufficiently charged, very common with the dual battery CLS. I would (and do) put the car on a trickle charge (Ctek are MB preferred units) every couple of weeks.

The issues with the AC and ventilated seats function does appear to be a fault and you are best advised to get the car on STAR and have the fault codes read. I know the seat heater/ventilation system will shut down if it detects and over-voltage and can't reset until IGN is cycled. The AC could be low on gas.

 

[RetiredSlider]

Thanks for the info chaps.
I'll look at ordering up another main battery and see if that helps things out.

Am i right in thinking that the heated seats, aircon etc are all powered by the main circuit and it's just the cabin lighting etc that's powered by the AUX Batt?

 

[whitenemesis]

The AUX battery is simply a back-up to the system battery in the boot and will be brought into service should the system battery go low on charge.

Nothing is directly connected to the AUX battery, everything goes through the BCM and system battery

 

[Alps]

as whitenemesis also states, if you don't use your car that often then get a trickle charger.

Give the main battery a good charge and then see if it re-appears over time

 

[RetiredSlider]

Thanks again for all your help.
I use the car daily and have done about 1800 miles in it so far with a couple of significant jaunts down to Bristol and I also drove it back from Preston which was a 4.5 hour schlep. I'm fairly sure that if the battery was going to get topped off, it would have done so during this time - however when checked neither the seats nor the A/C clicked on then either.

The convenience functions disabled warning comes up very infrequently. I don't see it during my usual driving. I saw it today due to the fact it was -2 outside when i started the car but i hadn't seen it for a while before that. The seats and aircon seem to be consistent tho.

 

[b1g1an]

The AUX battery is simply a back-up to the system battery in the boot and will be brought into service should the system battery go low on charge.

Nothing is directly connected to the AUX battery, everything goes through the BCM and system battery

It's only there so you have brakes if the electrical system packs up!

 

[RetiredSlider]

Brilliant,
Thanks guys - i really appreciate you taking the time to respond. Sounds like a new battery would be a good place to start to correct the problem. Can anybody recommend one or know what the correct spec is?

 

[Major774]

Most likely the battery needs a full charge off the car. The alternator is there to maintain charge and not to charge up the battery from a low state.

I was getting frequent convenience messages as my car was being used every other day on short trips. So i measured the voltage of the battery off the car, approximately 12.0-12.3v (measured a few times). The alternator couldn't charge the battery up to its full state of 12.6v+.

So I put the battery on a mains charger for 36 hours (got a low amp charger) and measured the voltage after I had removed the charger for 2 hours. It showed 12.6v+ (100% charged) and holding charge. It's has been in the car for 1-2 weeks and no convenience messages so far. The battery is new from Mercedes, bought in October 2014.

Out of interest, I just charged up my old battery (OEM 2011), it still holds charge and even passed a load tester. So I will just keep it as a spare and swap it over as an when needed, I think it's my driving pattern that is reducing the state of the battery over time.

 

[whitenemesis]

This MB tech training doc explains the dual battery system as used in the 211 and 219

https://www.dropbox.com/s/doiwpgwubkw1sff/319 HO Dual Battery (ACB - ICC) 11-29-02.pdf?dl=0

The dual battery system used in the R230 is different in that the under bonnet battery only connects to the starter motor. It has no other function.

 

[Major774]

Thanks again for all your help.
I use the car daily and have done about 1800 miles in it so far with a couple of significant jaunts down to Bristol and I also drove it back from Preston which was a 4.5 hour schlep. I'm fairly sure that if the battery was going to get topped off, it would have done so during this time - however when checked neither the seats nor the A/C clicked on then either.

The convenience functions disabled warning comes up very infrequently. I don't see it during my usual driving. I saw it today due to the fact it was -2 outside when i started the car but i hadn't seen it for a while before that. The seats and aircon seem to be consistent tho.

My convenience message would only come up on start up, it goes away after a few minutes. It's annoying as the heated seat function is disabled (the button will just flash) and the climate control is disabled as well... Not good for the cold winter mornings lol.

 

[Major774]

http://www.mbclub.co.uk/forums/engine/183618-battery-right-car.html

Check the outcome on this thread.

 

[RetiredSlider]

My convenience message would only come up on start up, it goes away after a few minutes. It's annoying as the heated seat function is disabled (the button will just flash) and the climate control is disabled as well... Not good for the cold winter mornings lol.

Interestingly, even when the convenience message goes away - the A/C and the heated seats don't come back up. Even when the message doesn't show the heated seats and a/c still don't work (just flash like you say)

 

[Major774]

Sounds more complex in your case