Convenience functions temporary unavailable

[MUNKSJOE]

Dear All,

My W211 E320 cdi 2003 has a new Varta main battery in the boot and a recon alternator just fitted but after 20 or 30 minutes of town driving the message Convenience functions temporary unavailable is shown and things like the air con blower motor stops working. I also have a malfunction message listed. I have checked the voltage gauge while driving and very quickly after starting it reads 14v and continues throughout the journey. Even with this healthy charge the message still appears. If I stop the car and turn off the ignition and wait a few minutes then turn on the ignition again the malfunction disappears and the process starts all over again.

This is happening when the weather is excellent and all I have on is the air conditioning. I did wonder if it could be the small battery under the bonnet but why would it happen while driving and charging and not from a cold start.

Any thoughts, ideas or suggestions would be appreciated.

Alan

 

[AMGeed]

Check the voltage of the Aux battery under the pollen filter. I bet its below 12.7v which is fully charged.
You can recharge these aux batteries but if its more than 4yrs old I'd get a new one.

Tayna sell a Varta one for half the price of a Fiamm OEM battery
https://www.tayna.co.uk/car-batteries/varta/mercedes-aux/

 

[MUNKSJOE]

Check the voltage of the Aux battery under the pollen filter. I bet its below 12.7v which is fully charged.
You can recharge these aux batteries but if its more than 4yrs old I'd get a new one.

Tayna sell a Varta one for half the price of a Fiamm OEM battery
https://www.tayna.co.uk/car-batteries/varta/mercedes-aux/

Thank you for your advise AMGeed,
I did have doubts about the aux battery and as Tayna have such a reasonable priced item it is worth a try. I have ordered one today.

 

[mersum1es]

If aux battery is dead and it draws main circuit and triggers the fault, its possible (check isolation relay too).

But convenience error is main battery related only, another possibilities are dying (new) main battery (not unheard), or faulty Battery Control Module BCM (prone to corrode). Also gorundings must be good everywhere.

And measure voltages from battery poles.

 

[onefortheroad]

Did they replace like for like alternators ,some cars came with high output types.

 

[mersum1es]

Alternator might be wrong type, then it is charging constant 14,3V, but AFAIK that should not trigger fault code for battery/convenience

 

[MUNKSJOE]

If aux battery is dead and it draws main circuit and triggers the fault, its possible (check isolation relay too).

But convenience error is main battery related only, another possibilities are dying (new) main battery (not unheard), or faulty Battery Control Module BCM (prone to corrode). Also gorundings must be good everywhere.

And measure voltages from battery poles.

Thank you mersum1es,

After reading up on this issue, both the aux battery and the BCM seem to cause problems. I have ordered a new aux battery today as it was not much money and my present one is original, so well past its best by date. Once its arrived and fitted I will see what happens. My smart charger has said my main new battery is OK but as you said new items do fail so I will have it tested where it was purchased. If these do not work the BCM will have to be looked into so I will be no doubt be back on the Forum for more help.

 

[MUNKSJOE]

Did they replace like for like alternators ,some cars came with high output types.

Thank you onefortheroad,

I made sure the recon alternator was an exact match, via numbers from the original and recon units. Both were Mercedes units. The voltage shown on the dash while town driving is minimum 14v, which I understand is good and should not cause problems.

 

[MUNKSJOE]

My issue has been Solved. All I needed was a new aux battery for the braking system, which is under the bonnet, of my W211 2003 320 CDi.

I think it is important to let the forum know after posting an issue how it was resolved as it could help others in the future. I would like to thank, AMGeed, mersum1es and onefortheroad for taking the time to share your knowledge.

Alan

 

[Botus]

Check the voltage of the Aux battery under the pollen filter. I bet its below 12.7v which is fully charged.
You can recharge these aux batteries but if its more than 4yrs old I'd get a new one.

Tayna sell a Varta one for half the price of a Fiamm OEM battery
https://www.tayna.co.uk/car-batteries/varta/mercedes-aux/

you can cut the top off this small aux battery to find 6 rubber bungs.... fill each with 25ml of distilled water and it'll be like new.... its job is to provide power to put the brakes on - when its all gone horribly wrong....

its not the failure that puts consumer message on.... how often do you drive the car? park for 3 week you'll get that message if you have fitted new batteries or not

 

[MUNKSJOE]

you can cut the top off this small aux battery to find 6 rubber bungs.... fill each with 25ml of distilled water and it'll be like new.... its job is to provide power to put the brakes on - when its all gone horribly wrong....

its not the failure that puts consumer message on.... how often do you drive the car? park for 3 week you'll get that message if you have fitted new batteries or not

Dear Botus,

The strange thing was that the message came up after 20 or 30 minutes of driving with a 14v charge showing on the dash. It would never show when first starting. If I stopped the car, turned of the ignition for a few minutes and started again the message would not show for another 20 minutes plus. This would happen time and time again.

My aux battery was the original. I know this as I have had the car from almost new and the date on the battery matches the car, I did think that as it was so old and as a new one was only £45 delivered I would give a new one a try. Your advise in topping up the aux battery is excellent but I thought at the time that it looked like a sealed unit. Luckily for me a new battery has worked.

Since retirement my car does tend to sit on the drive for days and even weeks but a trickle charger has helped. I am not saying a new aux battery is a remedy for all but I did find it strange that my problem did not show on start up. As you can imagine I am very happy that I have resolved a very annoying issue and I hope it may be of help to others.

 

[Botus]

My father has a w211 Feb 2006.

you get two red warning for low volt batteries...
one is the aux battery - with a warning about the brakes (and it stores the code too), I bought a new genuine one its gone away. But then I thought lets open it up and take a look....

the convince function one has become more and more prominent.... but then he's driving it less and less. Its stupidly dangerous as disables the washers and the demist fan.... crazy wiring!!! On some models there updates to the battery control module to reduce the nags, but I was told no update on his. I put another AGM in the boot and for 12 months the messages stayed away then just come back unless its driven every two weeks and or charged up. In 2 weeks of non use the rear battery will take 24 hours of charging before its topped it up again (which is the same in my car too).

I've got him in the habit of charging it regularly now - the message after you have been driving its interesting....