Electrical Consumers Switched Off ...?

[BigJon]

Hi,

I’ve had my ’03 E55 AMG for about 9 months. In the last 6 months I keep getting the following message on the dash :
"Malfunction Electrical Consumers Switched Off"

I took back to the dealer after the first couple of times and asked them to check the battery. They said it was fine and that I must have left something on, or left the car standing for an extended period.

I’m not convinced. I do 50 miles a day back and forth to work and shopping at the weekend. This week, its happened every day. Its getting more annoying as when it happens as it switches off the heating ! Which at the moment is a pain ! I don’t use the heated seated or anything excessive.

I understand the message means the auxiliary battery is low.

So, questions :

* Does this happen to anyone else regularly, is it a fault, or something I have to put up with ?

* Does anyone charge their car regularly ?

* Which battery is the auxiliary one ? the big one in the boot or the small one under the bonnet ? Can I just charge it normally with a car battery charger ? Has anyone done this ?

* While I searched the internet I found reference to this technical bulletin :
P-54_10-117 OCT 04 Electrical - Under Voltage Switch Off Consumers Message

Does anyone know if this is a fault, or a recall ? Maybe I have a bug ?

Thanks in advance

Jon.

 

[grober]

The auxilliary battery is in the boot. The small one in the front is for the starter motor. There were issues with some electronic control units flattening batteries which were the subject of MB recalls on the early w211s. There have been lots of posts about this on the forum. A former member called television was one expert on this and how to charge the auxilliary battery which I believe requires a different technique to normal batteries. Do a search and you will find more info. Havn't got one of these "electronic wonder" cars myself so can''t help any more than this sorry

 

[Diesel Benz]

The auxilliary battery is in the boot. The small one in the front is for the starter motor. There were issues with some electronic control units flattening batteries which were the subject of MB recalls on the early w211s. There have been lots of posts about this on the forum. A former member called television was one expert on this and how to charge the auxilliary battery which I believe requires a different technique to normal batteries. Do a search and you will find more info. Havn't got one of these "electronic wonder" cars myself so can''t help any more than this sorry

No, no, isn't this a W211 car? On the SL TV has the starter battery is at the engine bay and the main battery at the trunk (also on the W221).

On a W211 (pre-face-lift) the SBC backup battery is at the engine bay, under the cabin dust filter. The main battery is at the trunk.

A bad AUX battery is often causing these low battery warnings. But didn't they check both batteries at the shop?

2003 cars had a few charging related issues fixed through recalls, I guess the workshop must have checked these. It could simply be that you haven't driven enough with the car and/or left it parked for a ling time.

My guess would be the AUX battery or a control relay for that.

 

[grober]

My apologies. I had got it into my head that that the poster was talking about an SL! and didn't realise their position was different in a W211.
Found 2 recalls in the states that might be relevant?

Service Campaign 2005060008 JAN06
Programming battery control module
E (2003-2006) / CLS

Service Campaign 2005100009 NOV05
Inspect rear SAM control module, replace if necessary
E (2003)

As Diesel Benz says these should have been picked up by routine MB servicing. It depends if the car had slipped out of the MB recall/servicing system by that time. There should be a record of any changes/ module replacements in the cars service history. It might be worth asking for a detailed printout of the cars service history from your dealer. Your car may have slipped through the net?

 

[BigJon]

I may have found the problem. I decided to charge the battery to start with, and see if that made the message go away ... So, I dismantled the boot lining and when I got to the battery, I found the earth terminal was lose !?

So, either MB *didn't* test the battery when they said they did (or they would have seen the lose connector) or when they did test the battery, they didn’t put it back correctly.

Anyhow, battery now on charge over night, I'll see what happens next week.

One follow up question (to save me finding my user manual! ) I can't find the primary battery under the bonnet ?! The two plastic covers I can see either side have fuses and air conditioning under them ... can't see a battery anywhere !? Am I being blind, or is it well hidden ?

…. I’ve found a very large supercharged engine though ! That’ll be why it goes like stink !

 

[Diesel Benz]

Hopefully it was the loose wire.

I wouldn't call the battery under the bonnet a primary battery, it is a small one anyway. But you can find it if you first remove the AC dust filter housing.

 

[NewMB]

I have the same year on my E55 as BihJohn and the small battery in the engine bay (according to my dealer) mainly runs the backup system to the brakes but also some electrics. Not told if it also runs the starter motor.

The main battery is located in the boot.

I have had the same experience with a flat battery..... twice!

MB did a software upgrade on my SAM unit located next to the big battery in boot. Apparently, this unit decides what battery to use.

 

[Diesel Benz]

I have the same year on my E55 as BihJohn and the small battery in the engine bay (according to my dealer) mainly runs the backup system to the brakes but also some electrics. Not told if it also runs the starter motor.

The main battery is located in the boot.

I have had the same experience with a flat battery..... twice!

MB did a software upgrade on my SAM unit located next to the big battery in boot. Apparently, this unit decides what battery to use.

You don't have to read wiring diagrams, just look at the size of the AUX battery and you know it is not used to start the car.

The battery control unit takes care of charging the AUX battery too.

In addition to the above mentioned issues, the AUX battery relay failure is somewhat frequent.

But if both batteries are good and the charging works OK (battery voltage fine on both batteries when the car is switched off), the rest should be about quiescent current issues. Some are random and pretty difficult to identify, if the battery goes flat always after a relatively short time (car not used for a few days), then there must be some current draw that is not supposed to exist.

 

[Dieselman]

In addition to the above mentioned issues, the AUX battery relay failure is somewhat frequent.

I wonder what would happen if the relay was discarded and both batteries connected to charge simultaneously and run in parallel.

 

[Diesel Benz]

I wonder what would happen if the relay was discarded and both batteries connected to charge simultaneously and run in parallel.

You probably know the answer already, and certainly know better than me but looking at how the batteries are connected, it could almost work better without the relay.

I mean there are two separate fused power wires for the SBC control unit but these are not separately from the two batteries, the AUX battery can only supply the SBC unit (and the rest) once the relay is pulling and connecting the two batteries in parallel. Or did I get it wrong, only had a quick look (or the pre fuse box internal diagram isn't accurate).

Electronic consumers cannot make the AUX battery go flat when the car is not running, that is an advantage from the relay. I guess it makes the brakes work better after a flat consumer battery.

If I remember right, the starter battery e.g. on a W221 is charged completely differently, with a switching supply.

 

[trapperjohn]

Crikey bobs guys. TG I stick with "older" Mercs, may not be as much fun, but not half as much plumbin' to fathom either. Just thinking of moving on my C180 for a 124 3.0D 24V Estate. May the force be with the forum. CHEERS. Trapperjohn.

 

[Dieselman]

Electronic consumers cannot make the AUX battery go flat when the car is not running, that is an advantage from the relay. I guess it makes the brakes work better after a flat consumer battery.

If I remember right, the starter battery e.g. on a W221 is charged completely differently, with a switching supply.

I hadn't looked into this but think you are about right with your description.

The relay is there to isolate the AUX battery in case of a drain causing a flat battery, the SBC brakes will still function.

Seems like another good reason to avoid SBC...

 

[BigJon]

The dealer tested the battery again today during a routine service and it *does* have a problem. It had some cells failed. So it was the battery after all. I'm having it replaced. Hopefully that’s the end of it.

Its is a *very* annoying problem as it seems to happen more in the cold weather (obviously), and it turns off the heated seats and the heaters ! Exactly the two things I *do* need !? Why can't it turn off the interior lights, electric windows, radio, clock, etc. I'd rather be in silence than have no heating in the current climate !! I had to drive to work the other day in -4 deg, but I had the radio on !!

 

[jamesshipway]

The dealer tested the battery again today during a routine service and it *does* have a problem. It had some cells failed. So it was the battery after all. I'm having it replaced. Hopefully that’s the end of it.

Its is a *very* annoying problem as it seems to happen more in the cold weather (obviously), and it turns off the heated seats and the heaters ! Exactly the two things I *do* need !? Why can't it turn off the interior lights, electric windows, radio, clock, etc. I'd rather be in silence than have no heating in the current climate !! I had to drive to work the other day in -4 deg, but I had the radio on !!

Hopefully you'll have it all sorted now since it's very cold Just out of interest - was it the auxillary battery at the front or the main one in the boot that needed replacing??

 

[BigJon]

The big one in the boot.

 

[Hal Adams]

BigJon - you appear to be shouldering a lot of problems with such a fine car. Echoing a previous post, you are doing well in taking the extended warranty.
BUT, I would be very upset if a dealer told me that my battery was fine, only to go home and find the terminal loose (obviously your underlying problem) and then, on return, to be told 'oh, yeah, there are some dead cells'.
If a dealer gets this wrong, what chance has he got doing something really tricky like timing belts or crankshaft sensors - and this before we get into the really complex area of electronics...!
I would really want to take them to on side and tell them to take things a bit more seriously, especially in these times...I am sure there is another dealer close by...

 

[BigJon]

Fair point. I will have a chat with them when I go in to collect my car. However I'm not sure about the "dealer close by" bit ... This one's already nearly 20 miles away and that my closet !

 

[MBLover247]

I am an MB E240 AMG W211 user for quite a long time now.Recently I have been getting these messages of "Electrical Consumers Switched off".I did not pay much heed to it.I kept on driving and then all of a sudden one day all the inside lights went off,then the windows stopped working. What could be the reason? I changed the battery recently seeing the forum's post but it has still not brought my lights back.My windows are still unoperational.Can somebody help please....

 

[MBLover247]

Also,can someone enlighten me about the actual use of the front small battery as to what it does and what happens when its not there?

 

[merc85]

Also,can someone enlighten me about the actual use of the front small battery as to what it does and what happens when its not there?

The Aux battery is a provission in case the Main battery discharges completely as a back up for the SBC braking system.

As i understand it if the small battery is not there and the main battery go's flat for example a duff alternator the vehicle would have very limited braking power

"i may of course be wrong"