Good morning, so my issue is my 1.4 auto 6n polo isn't charging, after a very sparky jump start a few weeks ago a few things got a bit hot and melty, the main fuse fried and I suspected the alternator took a battering, so I replaced the alternator with a new unit replaced the main fuse (alternator) and charged the battery .. on refitting .. I'm getting 12.4v off the battery and when I run the car I take a hit to just over 11 .. not the juicy 13 - 14v I was expecting .. is there anything obvious I am missing? im fairly sure the 12v regulator is part of the alternator, alternator is fitted as it should be with correct tension etc .. am out of ideas.

many thanks in advance

Does the battery light come on when you turn on ignition?

If it is 3 years or older take the battery for a deep discharge test. I suspect one cell is not doing its job.