Right, two weeks ago got the garage to change the alternator on my 56 plate Focus TDCi, all seemed okay for a couple of short trips, then i took it for my work commute (about 55 miles) and pulled up off the motorway with smoke coming from the engine bay.
Called the RAC, was diagnosed as the drive shaft pulley into the alternator that had broken - the rubbers had been ripped up (somehow) RAC man replaced it - at a big cost, all seemed fine - drove home, pulled up at house and same thing happened, smoke, called RAC - drive shaft rubbers ripped apart, again.

anyhoo, managed to nurse it to the garage and they are now looking at it. Replacing the alternator and drive shaft/pulley. except they are having problems, they don't want to give the car back until they've found out what's causing it. Could it just be mounted incorrectly / spacers or something?