Since I am eliminating causes for my battery drainI hooked up a voltmeter on the battery poles. In the meanwhile running the engine in idle and using all electra available in the car (seat heating, prog button, airco, screen heating, lights and fog lights you name it). The readout came to 11,4V... shouldn't it be approx. 14V. Is it a correct assumption that the alternator appears R.I.P. aka gone bad... It does also make alight grindingzooming in the area around the alternator...

 

If your battery is in really good order, the output will be less than maximum from the alternator, if it is in a state of half discharged, the output will be higher from the alternator. so, it depends...

So after checking battery condition, all starting/ignition wiring connections, earthing, drivebelt tensions, do the following...

To verify alternator performance, follow the procedure for checking the alternator in your haynes manual,
- you will need 2 test meters for convenience! - one for the amps, & one for the voltage, it will help if you have a 2nd person to assist in the drivers seat with the revs as the readings will need time to settle.

**be careful where the large brown disconnected lead from the alternator is allowed to travel when you do the tests.**

The grinding/zooming noise ... is your alternator drive belt too tight? - a 1/4 inch deflection in middle oflongest run on the drivebelt is normal.(also, check the noise suppressor!)

Good luck...