W211 red battery warning and varying voltage

[bigdieselfan]

Just wondering if anyone has come across this version of the red battery warning. Shortly after starting my 2003 W211 E320 CDi the red warning symbol pops up stating that a visit to the workshop is required. After that I get a note about the convenience functions being unavailable. Thanks to this forum I've found out how to get the voltage displayed and here’s what it shows:-

Key still in position 1: 12.2 volts
After starting and at idle: 11.9 volts

10-15 seconds after starting the red warning comes on. The volts stay around the low 12’s from idle to 3,000 revs, but I’ve found that once the revs go past 3,000 rpm (even if briefly) the car partly sorts itself out and it shows 13.9/14.0 volts, even at idle. 15 seconds or so after this the convenience functions are available again although the red symbol remains. If I stop the car and restart it within a few minutes of stopping then it will start with no red warning or malfunctions. If it’s a longer stop though, say more than 10 minutes, then the red warning reappears shortly after starting.

The car had a service recently and both batteries were checked and found to be OK.

Any thoughts on what is most likely to be causing this problem? Thanks again, for a top forum.

p.s. for anyone who’s not come across other posts about how to get the voltage displayed (in a W211 at least), turn the ignition to key position 1, put the display to temperature and then press the dashboard reset button 3 times.

 

[Satch]

Hmm, mine will go to 13.8/13.9 volts at idle.

Number of possible miseries but equally you will get those "protection" messages with an infrequently used vehicle, especially in cold weather.

If you look here it explains how it all works and the protection stages

http://www.mercedestechstore.com/pdfs/W211_advisor/219 HO Dual Battery (ACB - ICC) 11-29-02.pdf

I use CTEK charger (wired up with tags to the main battery terminals with an extension cable to make life as easy as possible) if car is not going to be used for a few days.

 

[mct_cars]

Get it on STAR. Could be as simple as voltage regulator / alternator.

 

[bigdieselfan]

Thanks Satch and MCT. I'm still a bit stuck so have booked it into an Indy to get it on Star. Thanks again for your help. Will publish the outcome.

 

[bigdieselfan]

Hi, just in case anyone has the same problem the problem and outcome was:

Problem: red charging warning light comes on shortly after starting.
Other info: having the voltage displaying showed that it initially it was around 12 volts. I guess it was either not putting out anything or just the 12 volts.
After a while, sometimes 10 minutes or when the revs went past 3,000, the voltage went to around 14 volts and stayed there.

The Indy put it on Star but couldn't tell me if it just the voltage regulator or if it required a new alternator. To be sure they suggested the latter for £500 fitted.

In the end I went to MB and bought the voltage regulator for £70 and got the Indy to fit it for £170 and it's resolved the problem. No more red charging warnings and convenience functions available from the start.

Thanks for your help.

 

[optsef]

Just to follow on from this, I had the same problem but progressed to the display showing "brakes defective-STOP". Local (Blackpool) Indie diagnosed faulty voltage regulator on alternator and replaced for total cost of £140. Problem solved.