As above had a bit of a problem recently and its to do with my alternator or battery or something

Basically the cars had a new battery about 3 months ago so i think i can rule this out

Now what does the little blue wire on the alternator do ? something to with batt light ?

Went to my alernator tonight and re-done my connections and also this blue wire connection ? , i moved it to another bolt on alternator ? now my batt light stays on ? easy changed back i suppose

Now previos to this with my car running i was getting 11.36v on the batt terminals , now after redoing my connections and cleaning some stuff up , i jump started car and now on batt terminals with car running im getting 13.56v ? and switched off about 12.67v ? dunno i fixed my problem ? but are these readings about right and also would i need to change this wire over to get light to go off ?

any help appreciated as its like pissing in the wind with probbs like this ?