W639 battery warning light

[Steeelyglint]

Hi looking for a bit of advice.
Battery light is coming on about a minute after starting my Viano. 2008 model. W639.
A volt meter in the cigarette lighter shows it's charging the battery at about 14.6 v and my ring smart battery charger also gives it the thumbs up. The garage is stumped I. E. The signal wire appears to have continuity etc. I have replaced the 2008 battery but the fault persists.
Is there a way to check whether it's an alternator fault without fitting a new one. I. E. Mimic the signal the alternator should send when it's charging to see if that switches the light off? I'm not electrically minded so idiots guide patronising tone welcome!

 

[optimusprime]

I would have a new regulator fitted in the alternator ..really there is nothing much in the alternator to go wrong , regulator can be replace without the need to remove alternator from the engine .

 

[Steeelyglint]

I would have a new regulator fitted in the alternator ..really there is nothing much in the alternator to go wrong , regulator can be replace without the need to remove alternator from the engine .

Thank you. The alternator was replaced a few years ago by a local garage so not sure if an MB regulator part would fit. Is there a simple check to prove it is the regulator rather than the engine mgt. unit?that the alternator sends the signal to?

 

[optimusprime]

Power goes to central control box, and also the alternator Lin Buss could be a communication fault .This is only what i have found doing a search .. It would be a cheap fix to replace alternator regulator brush box , something you could do at home .

 

[Steeelyglint]

Ok I'll have a go thank you.