E350 not charging

[keith of kent]

2015 E350 71k miles
Whilst driving a schematic of a battery came up on the speedo display saying "Consult drivers manual". Tried to use the on screen handbook without success. Engine still running so drove 15miles home keeping an eye on the temparature gauge.
After a while Command shut down, otherwise driving as normal. Checked the battery voltage with multi meter 12v with engine off and 11.6 with it on although at that moment the coolant fan came on. Temp gauge still at 90 degrees.
Waiting for my Indy to call me back. No signs of anything amiss in the engine bay. When I restarted the engine the display message cleared but soon reappeared.
Have put the battery (which is a 3 year old Varta) on charge with my Accumate.
Sounds like the alternator?
The auxillary batery is about 2 years old also a Varta

 

[ALFAitalia]

Should be 12.6 with engine off......14 plus with engine running....dead alternator most likely.....but it could be lose connections or very poor grounding.

 

[keith of kent]

Once home I accessed the on line instruction manual which says it could be a faulty alternator or a broken V belt, and not to drive as the engine could overheat. Is the drive belt for the alternator separate for the one that drives the alternator? And on my return journey the air con was blowing cold as required

 

[keith of kent]

An update but sadly still got problems.
Had to wait a week before the local Maidstone INDY could take the car in and they said it was the alternator. He said that aftermarket ones "don't last long in a mercedes" and therefore should fit a genuine one , £620 + vat plus fitting, just over £1200 !!!!!
So after another few days my wallet had been lightened and I got the car back. All seemed ok until I spent a short time with just Command on to input some sat nav destinations, then Command shut down unless I started the engine.
Ran the engine for 5 minutes, turned it off and after 10 mins Command shut down. The battery at this point was showing 11.9V with engine off and over 14v with it running. So charging.
During the course of all this I refitted the original battery yesterday, had charged it to 12.9V Took the charger off last night 12.9v with engine off.
Aso this morning battery is down to 11.9V, now on charge (engine will still start)
I noticed that when refitting the second (negative) battery terminal connection that there was a slight spark from the terminal .
Everything was turned off, key out and doors shut at this point.
I'm thinking the there is a parasitic drain on the battery.
I will be very gratefull for any suggestions
Thank you