W211 Battery Voltage Running High

[m dev]

Would appreciate some help please. Had a RED battery warning signal and on checking the voltage, at idle it is around 11.5 but strangely when engine started, it starts to shoot up and goes up to 16.4V before the RED warning signal comes on and all convenience functions turn off.
Clearly this is too high and will damage the circuits if sustained. Any ideas on what maybe causing and how I may identify?

- Overcharging alternator?
- Faulty voltage regulator?
- Battery control module?

 

[Flyinspanner]

Get the output on alternator checked, sooner rather than later. (ASAP)
That does sound like an alternator issue.

 

[Silver_Star]

More then likely the voltage regulator/bush pack on the alternator.

 

[bigasotonuk]

Hi
Plus one for the Alternator regulator brush pack, they are approx £50 from the dealer (i think) guaranteed fitment from dealer, almost certainly can sourced aftermarket but they will need to know exactly make/model of Alternator fitted.
As long as you have reasonably clear access to the back of the Alternator then it can be replaced in situ, just a couple of screws/bolts and electrical connections, do make sure you disconnect "both" batteries before replacing.

 

[m dev]

Thanks all. Voltage regulator it was. All replaced and sorted today. All done for £75.

 

[bigasotonuk]

Thanks all. Voltage regulator it was. All replaced and sorted today. All done for £75.

Hi,
Just for completeness were you able to replace it with the Alternator in place?
Did you buy OEM or Aftermarket? How much was it?