I have just replaced the alternator on my 1.9tdi, however it is not holding a charge, prior to change of alternator the battery light came on , I jump started a car , could I have blown a fuse or relay as I dont think it is the alternator

there is a fuseable link for the charging systen in the box that is mounted on top of the battery it has been known for the 10mm nuts to work loose that hold the fuse in place and then it melts the fuse holder