Gremlins

My alternator saga continues.....

After looking at the 'load sense wire' and finding out it was ok, i looked into getting a new (well, second hand) alternator, so popped off to the local scrappy and got a 90amp the same as mine, fitted to the car and wallah, worked, drove ten miles to charge battery a bit, fuel up and park for couple of hours, go out later on, drive it three miles and the alternator goes again... Is it just me?? Now, waiting on a mate to jump me to see what the charge voltage is now, but do you think i got 'just' another faulty alternator, it was seized which i didnt notice but it free'd up and charged fine for couple of hours, think i overloaded it cause it aint been used in ages, i had everything on in car as -5 outside and dark.... Might go get another tomorrow but dont want it blowing up again, any ideas as to what could be going wrong here??

regards