Alternator fault- battery not charging

[Sparky_143]

Hi all,
Driving home from work today and got the message 'alternator fault- battery not charging'
Checked the battery level and it was at 70%.
In start stop traffic the battery was dropping and the revs wouldn't go below 1000
Turned off heater, radio and lights hoping this would help the battery level as it was dropping quite fast
The level got to 10% and I feared the worse.
Then, the message disappeared from the display and the battery started charging and the revs went back to normal.
By the time I got home the battery had reached 90%
Has anyone experienced this problem? Is this just a little glitch or do you reckon the alternator is on its way out?
Want to price up a new one just in case, does anyone know the rating/ part number for an alternator for a 2008 2.0tdi.
Thanks.

[Alan02]

You need it diagnosed properly rather than putting parts on and hoping for the best.
I guess your model may have a control box at the battery to monitor battery condition, if so, this should be included in checking battery and charging condition.