Problem with 2007 XJ Sov 2.7 tdi

[330p4]

Battery warning light started to come on and off intermittently now on most of the time. Voltage was about 12.4V with engine off with engine running it was 13.5V I know the alternators are a smart charge which is load dependent I changed the battery as it was 7 years old still the same any other suggestions other than alternator ? I will check engine earth to body as it is providing some charge I don't think it can be a fuse I believe the charging is temperature dependant as well as load where is this temperature sensor any help appreciated
Ian