Hello, 

need some advice, I got a new Bosch alternator in June 23, car broke down 2 weeks ago so went to the same garage as alternator was under warranty. So had the alternator replaced and drove the car for a week. Again the same issue 12v battery not charging sign on dashboard so went back to the same garage and they said to change the battery so got a new Bosch battery as well. Drove the car for a day and again the same warning light 12v battery not charging. 
so after having a new Bosch alternator and Bosch battery why is the fault coming again?  Waiting to see the garage again on Monday so let’s hope to get it fixed.

any advice, thanks

You need a capable garage. If the garage cannot even diagnose the difference between a failing battery and a failing alternator, they are useless and should stop calling themselves a garage.

Simply connect a multimeter to a 12V line and measure the voltage. With a running engine that should be around 14V. If it is around 12V, than your battery won't charge, and their is something wrong with the alternator or the voltage regulator.

Thanks for the reply, you are right. They didn’t connect the alternator properly, something wasn’t connected and there was oil leak from oil filter as well. So went to different garage and they removed the alternator belt and opened alternator and connected switch like something which was loose. Apparantely they paid for that labour and breakdown and I still paid for the new Bosch battery which costed £290 with vat. So I’ve been driving the car since a week now with new Bosch alternator and Bosch battery and no problem till now touch wood. Thanks for the reply though.