2006 CLS 500 "dead"

[Big Bad Boris]

Hi people,

Just returned from holiday (3 weeks)left the CLS in the garage, with the battery connected. Just tried to fire her up and she's as dead as a dodo. I opened the door with the key but when putting the key in the ignition...nothing.

Is it as simple as the battery being flat or could it have shut itself down to save power (my 911 used to do something similar but leap into life when the door was opened manually)if so how do i get it back to life.

Any suggestions.... or simply charge the battery?

Thanks for any sugestions,

BBB.

[r129sl]

Come on, the battery has to be the first port of call, doesn't it?

[Big Bad Boris]

Well yes - but my tin pot Peugeot started first turn of the key after the same period of time. I never had any issies with the 911, as i said it used to put itself to "sleep" after a couple of days. Given the Merc is a newer and equally as German I wondered if something similar had happened.... got to about page 798 of the manual last night but didn't find anything useful. I guess Mercs don't sleep, they just kindly run their batteries flat?

[vilus]

Certain Mercs, especially E class W211, on which the CLS is based are notorious for flattening their batteries. I would never dream of parking my E class at the airport and jetting off for a holiday as I used to with my BMW's. I had to call Mercedes Assyst after leaving my AMG for a week at my sisters in London and they had to replace the main battery as it was dead and wouldn't even jump start. I've heard stories of W211 batteries going flat after just a couple of days.

[vilus]

PS. If the car has SBC braking there will be a secondary battery under the bonnet. Charge or jumpstart the car from the main battery in the boot. If the battery is completely dead leave the donor charge car idling and connected for about five minutes to stabilise before attempting to start the car. Once you get it started, while idling, turn the steering from lock to lock. This resets the ESP system and avoids error mesages on the dash.

[kevinpsw]

I haven't had the problem (yet) with my 07 CLS but my 04 CLK did the same several times. I had the battery (the third since the car was new) tested twice and declared fit. Mercs of that generation just don't like being left idle. Not sure about newer models.

[Big Brin]

If the CLS follows the format of my SL55 the battery that starts the car is the smaller one under the bonnet and the larger one in the boot is the one that services all the electrics (like the locking etc). You should not jumpstart the one in the boot.....as it will screw the electrics big time. The one under the bonnet can be jump started and the one in the boot will charge once the car is running again.

Rgds, Brin

[mbtech01]

Your CLS has many control modules on it that control all the systems on your car. When locking it, it should go into sleep mode & shut all the systems down. However if the general condition of the main battery is poor then it will only weaken over a period of time & non use leading to the problem you've experienced.
First port of call would be to get the battery in the boot checked out, i'd lay odds on its past its sell by date & time for a new one. If it's ok or you have it replaced & still experience problems have a current drain check done on your vehicle in the fully locked state to make sure nothings causing a drain.

[vilus]

Big Brin said:

If the CLS follows the format of my SL55 the battery that starts the car is the smaller one under the bonnet and the larger one in the boot is the one that services all the electrics (like the locking etc). You should not jumpstart the one in the boot.....as it will screw the electrics big time. The one under the bonnet can be jump started and the one in the boot will charge once the car is running again.

Rgds, Brin

SL owners manual instructs you to jumpstart from front battery, however E Class and CLS owners manual state to jump from main rear boot battery, so I guess there are some differences, maybe to do with limited boot space and folding roof on the SL.
The CLS/ E Class auxilliary battery is not even visible, located under the A/c filter next to windscreen on drivers side, and is a small 45 amp item and would not be able to crank the engine and supply the ECU etc without charge from the other battery. When I was stranded at the roadside both batteries were flat and the car could not be jump started needing the large battery in the boot replacing.

Edited by vilus on Saturday 1st September 20:03