Hi, I recently bought my mondeo and when i first started it it was struggling to start and was very noisey from where the altenator is .. I havent took it back to the garage yet but i have notified him of it. Then this morning my car started as usual and i drove it for around 20mins then i nipped out in it and it wouldnt start like my battery was dead, so i get a jump start and whilst it was running i tested the battery to see if my altenator was doing its job amd with everything off but the engine it was around 12v then once i put my side lights on and heaters and it dropped to 10v. Does this mean my altenator is going or could this mean i just need a new battery. its worth mentioning that the battery is the original battery from 2006 and is a calcium battery.

Any advice would be much appreciated because if it is the altenator it should be covered by my warrenty

Thanks