W203 Electrical Malfunctions

[JJ1989]

Hi guys,

Was wondering if anyone could advise on the following issue I'm having on my 03 C Class Coupe. Recently when starting the car I'll be presented with various electrical malfunctions such as SRS, ESP or Automatic light sensors on the dashboard. These will usually disappear after a few minutes once I've adjusted my seat and the car has warmed up a little, there are no faults with these components and the car performs as it should. Now all of these issues lead me to believe there must be an electrical fault somewhere in the car. I've had the battery and alternator checked and both are fine. In the recent cold weather I've noticed a lot of condensation in the car (especially the windscreen) before getting in and wonder if it could be linked to dampness?

Any suggestions would be greatly welcomed!

 

[John Laidlaw]

Alternator would have been my first thought, and these only have one battery so if that's checked out I'm not sure. Hopefully some bright spark will be along soon.....

 

[malcolm E53 AMG]

Welcome!

My first thought is that the battery isn’t holding charge overnight and the voltage drop is causing the malfunction lights to come on, when the alternator puts some charge into the battery the lights go off. MBs are very sensitive to low voltage so I suggest you put a meter across the battery terminals before first start of the day it should register 12.6V if the battery is healthy if it’s 12.4V or less you have a problem and it will need replacing.

 

[sonic]

If you can leave it on charge overnight, if it starts in the morning its almost certainly the battery. First bit of cold weather always shows a weak battery.