I hope I can be helped

Nov 2, 2009 | 02:20 AM

shegel

Thread Starter

Newbie

Joined: Nov 2009

Posts: 5

Likes: 0

From: Bonney Lake, WA

2004 E500

I hope I can be helped

Hello my name is Steve. I was on a different forum but all they said was become friends with my local mechanic.... I come from the vw scene where you are your own mechanic. I have searched but I didnt see anything that matched the problem close enough. anyways the car is a 2004 E500 sport Here's my problem

on my parents dash display we get the battery symbol and the "visit workshop" They have no other problems other than this warning. The vehicle starts and runs fine. I checked the voltage at the rear main battery and it reads 14.2v. The only thing I have done differently today is, I figured out how to turn the fogs on.

They haven't had the car for very long, I didnt push the knob back in before I turned the headlights back to the auto position, if that makes a difference. They are both school teachers and saved up for a long time to buy there new used mercedes

any help is appreciated

thanks,
Steve

Nov 2, 2009 | 03:53 AM

ap10046

Super Member

Joined: Nov 2008

Posts: 620

Likes: 16

CLS500 M113

Hi Steve,
had the same red screen and warning last week. It is most probably the small auxillary battery under the hood.This is the backup for the SBC system in our cars, not there in the post 2005 ones. Changed it and the malfunction/warning is now gone.
Hope this helps
Areez

Nov 2, 2009 | 06:45 AM

Clinton Horn

Senior Member

Joined: Sep 2006

Posts: 413

Likes: 3

2003 E320

The aux battery is located beneath the cover on the passenger side of the engine compartment near the firewall. There is a sticker that says "battery in trunk" or something similar. If you remove the lid, there is a filter for the A-C system and the battery is below. If you search this forum under aux battery you will find plenty of helpful advice. There was(is?) a recall on the alternator / voltage regulator that may also be the culprit. That may be a freebe. The aux battery is a small rec vehicle type that can be sourced from lots of places. Expect to pay about $70. You should be very careful about the installation. Grounding the positive terminal while installing is reported to cause some extensive damage. Look for a set of instructions posted by vettdrvr (screen name). They are very helpful about the sequence. Disconnecting the main battery is recommended. That requires re- programming the sunroof etc. Still, this is an easy maintenance item and has been reported as high as $400 at dealers. Good Luck

Nov 2, 2009 | 08:27 AM

paulv

Super Member

Joined: Apr 2005

Posts: 666

Likes: 4

From: Boston, MA USA

03 E320 -wife's car now; 07 Porsche Boxster S - my toy

Quote:

Originally Posted by shegel

.............. I checked the voltage at the rear main battery and it reads 14.2v. ............

At 14.2 volts, it sounds like you tested the battery with the engine running. You need to test with the engine off (no charging). Shut off ignition, and turn the lights on for a couple of minutes to remove any surface charge on the battery and then shut them off -- do the test. The AGM battery should read 12.6-12.8 volts. Test the aux battery with the key off -- can't remove a surface charge. The test should read the same 12.6-12.8 volts. The aux battery is only charged when the battery control module commands it to be charged.

Regards,
paul...

Nov 2, 2009 | 02:18 PM

shegel

Thread Starter

Newbie

Joined: Nov 2009

Posts: 5

Likes: 0

From: Bonney Lake, WA

2004 E500

paulv, I checked the voltage while the car was runing to verify that the alternator was charging. I realize that the voltage should be about 12.5-12.8 while it is off I didnt check that though and will as soon as my parents get home from school.

If I read correctly the aux battery is a 14bs. or somthing similar to that?

thanks though,

Nov 2, 2009 | 02:46 PM

paulv

Super Member

Joined: Apr 2005

Posts: 666

Likes: 4

From: Boston, MA USA

03 E320 -wife's car now; 07 Porsche Boxster S - my toy

Quote:

Originally Posted by shegel

..................................
If I read correctly the aux battery is a 14bs. or somthing similar to that?

.............

Seems like a 14BS will work as others have stated -- I bought mine from the dealer a few years ago and didn't go looking for alternatives.

It is important to remove the surface charge on these (AGM) batteries before taking any test readings as I mentioned before of the numbers will be off.
Regards,
paul...