alternator probs causing 200Tdi battery discharging

further to my previous post about my battery discharging overnight,I have narrowed it down to the alternator.
with the positive lead off the battery I connected a meter between the possitive lead and the possitive post on the battery and I had a leak of over 3amps
after a sugestion by a forum member, I un plugged the three pin plug on the back of the alternator and put the meter back on. no leak. plugged the alternator back in and leak is back.
OK so what do you think could be the problem and what do you think I should change?

The diode is most likely to be at fault. You should be able to get it seperately rather than having to buy a complete alternator.

Like I said in the other thread its the diode pack.

hope you have got a bloody good soldering iron to change it

look for my thread on this and you will find a cheap alternative