W221 Comand warning.

[gus0898uk]

On my 2006 S Class I am unable to listen to the radio without the engine running as a Comand 3 minute warning comes up. Is this a battery problem? I have no problems or hesitation when starting the car but I have noticed that if I wind the windows up with the engine off, they go up much slower than when the engine is running. TIA.

 

[markjay]

COMAND will switch itself off if the battery voltage goes down below a certain value and the engine isn't running.

So either the battery is indeed weak, or there's a fault somewhere and the system thinks the voltage is low while it isn't.

The former is the more-likely explanation.

 

[gus0898uk]

Thanks very much for that info markjay, I will get the battery checked out in the next couple of weeks.
I imagine Comand comes via the main battery and not the accessory one.

 

[Diesel Benz]

Thanks very much for that info markjay, I will get the battery checked out in the next couple of weeks.
I imagine Comand comes via the main battery and not the accessory one.

I would say the main battery is the accessory battery. The other one is for the starter only (obviously the consumer battery, the bigger one on a MY 2006 car, supplies Comand).

 

[gus0898uk]

I would say the main battery is the accessory battery. The other one is for the starter only (obviously the consumer battery, the bigger one on a MY 2006 car, supplies Comand).

Cheers Diesel Benz.
OK, so I don't **** this up, my car starts as good as gold every time, my Comand let's me know it is going to shut down in 3 minutes when the radio is on and the engine is not running.

In all probability, is it the accessory battery that is likely past it's best?

 

[zipdip]

Yes it is the battery behind the rear seats entry from the boot.

 

[gus0898uk]

Thanks to the forum members for your help.

 

[gus0898uk]

I have just had an after thought.
(There is no Comand Battery Warning message on my dashboard)
My Comand warns about switching off in 3 minutes with the engine off, but I am sure I have seen a warning message at some stage in the Comand/radio screen that I need to drive a long journey. I do make almost totally short journeys, so this could be the problem.
I could charge the rear battery but given it is not easy to access for an older person I am first going to give her a nice run out to charge the systems, this could save me buying a new rear battery.
Once again thanks for your help all.

 

[zipdip]

Well a long run may charge the battery up,but if you can access the rear battery,I take out the boot floor covering very simple and I remove the left soft boot cover,you need to disconect the left boot light and a couple of screws,then you can remove the hard back of the rear seats,and the battery is very easy to slide out once you disconnect it,or put a battery tester on it,I have a cheap one that tells you the state of the battery,in many cases it is just the age of the battery that has reduced its charge holding over time,if you replace it make certain you get the exact same one.

 

[gus0898uk]

Many thanks zipdip

 

[Skd884]

I would give it a slow charge.

 

[gus0898uk]

 

[Diesel Benz]

Well a long run may charge the battery up,but if you can access the rear battery,I take out the boot floor covering very simple and I remove the left soft boot cover,you need to disconect the left boot light and a couple of screws,then you can remove the hard back of the rear seats,and the battery is very easy to slide out once you disconnect it,or put a battery tester on it,I have a cheap one that tells you the state of the battery,in many cases it is just the age of the battery that has reduced its charge holding over time,if you replace it make certain you get the exact same one.

One should not need to remove the floor cover or the side panel(s), the panel behind the rear seat should come off without tools. An exception if you have the rear fridge or through loading door that needs to be removed first.

There is a charging pole for the rear battery at the engine bay. The pole is hidden behind a small plastic panel. No need remove any boot panels to be able to charge the rear battery.

 

[gus0898uk]

Thanks Diesel benz I will see if I can locate the charging pole.

 

[gus0898uk]

OK BM's
I gave the accessory battery a slow charge using the method given to me on here via the plastic box next to the under bonnet battery.
Once the rear battery was showing full, I sat in the car to listen to the radio with the engine switched off, and sure enough after a few minutes a notice came up on the display to say Comand would be shutting down in 3 minutes.

Is it normal to be able to listen to the radio with the engine off for just 5 minutes or could I have a fault in the Comand? TIA

 

[Diesel Benz]

I don't think it is normal. If I remember right, the car switches Comand off after 20 or 30 minutes. Did you measure the rear battery voltage when Comand turns off? Perhaps consumer battery kaput.

 

[mercmancdi]

Did you ever try letting it shut down and then turn on with button to see if it runs then without message.
I had Toyota when I parked turned off engine it always shut down after a few minutes but by switching back on it would run for ages .
Sorry if this has already been suggested or tried.

 

[gus0898uk]

Thanks for the tips Diesel Benz and Mercmancdi.
I will keep you informed but now it is raining, and I also had one too many last night so I feel a tad fragile.

 

[gus0898uk]

Update time
I am no Toto Wolff so please excuse my lack of motoring knowledge. I bought a cheap multi meter but have never used one before but where there's a will there's a way.
So my front battery showed 13.07 and also my rear battery showed the same 13.07 yet when listening to the radio without the engine running, Comand warns me that it will shut down in 3 minutes.
I seem to remember I once missed this message and the Comand shut down, but when I restarted the car the problem wa still the same.
Do I assume correctly that the 13.07 is OK for both batteries?
TIA

 

[markjay]

Update time
I am no Toto Wolff so please excuse my lack of motoring knowledge. I bought a cheap multi meter but have never used one before but where there's a will there's a way.
So my front battery showed 13.07 and also my rear battery showed the same 13.07 yet when listening to the radio without the engine running, Comand warns me that it will shut down in 3 minutes.
I seem to remember I once missed this message and the Comand shut down, but when I restarted the car the problem wa still the same.
Do I assume correctly that the 13.07 is OK for both batteries?
TIA

13.07v with the engine running? Or with the engine switched-on?