Red battery light

Hello I have a discovery 2 td5 for the last couple of days on start up when I put key in ignition all lights come on apart from the red battery light took it to get a voltage test done switched of I have a reading off 12.3 when started at idle I have a reading of 14.2 so that tells me the alternator is sending enough power and working as it should sometimes the red battery light comes on when I go to start it but sometimes it dont come on no issues with starting the td5 it has alway fired up 1st turn since having this issue it don't stop me driving at all as done about 150 miles or so since its been doing this and also when driving I don't get no flickering light but this morning when I started up no red battery light on dash so gave it a thew up done I the throttle to around 2500 to 3000 rpm then switched off then nd then switched back on nd the red light appeared I'm a bit lost now as to what direction to go to now any ifo would be much appreciated thanku

Make sure that the small plug on the alternator is well connected.... turn ignition on 2 and jiggle it while somebody is watching the dash and if it comes on there's the problem... if no joy we'll speak again..... meanwhile if you don't have it download the necessary docs compatible with your vehicle's MY https://www.dropbox.com/sh/47hbz40an5he5j2/AACH509eV_o7QhM5PoX6eFVLa

Make sure that the small plug on the alternator is well connected.... turn ignition on 2 and jiggle it while somebody is watching the dash and if it comes on there's the problem... if no joy we'll speak again..... meanwhile if you don't have it download the necessary docs compatible with your vehicle's MY https://www.dropbox.com/sh/47hbz40an5he5j2/AACH509eV_o7QhM5PoX6eFVLa