Santos,
The alternator should be putting out around 14.5 volts. It's obviously not energizing the alternator, which equates to not charging your battery. Have you changed anything in your dash? Do you still have the oil pressure warning light going to the sender? The reason I ask is that I've had the same problem. My brown energizer lead went open, and charge light stopped working. I temporarily connected a jumper wire from my oil pressure warning light to the energizer lead on the alternator.
It actually started charging. Don't cut the plug.
You can check the ohms coming from the charge wire. Do a search on the site, and you'll find a whole thread on the subject.
It will cover checking the lead for resistance.
BTW, IIRC, I ran a new wire to replace the brown lead that tested open. I think I connected to a switched +12 volt source on the fuse box and used a resistor (from Radio Shack) inline. I didn't buy the adapter plug. I didn't cut any wires. If anything, I used connectors.
I'll almost guarantee that the alternator is not being energized, especially that you said it tested okay.