It's the alternator internal regulator. Stop searching and change it. Go to any good alternator rebuilt shop and order this :
Transpo : IN218 - ±30$ (
http://195.125.241.148/cgi-win/product.exe?IN218)
Or go at your Toyota dealer ans order :
3B 12V voltage regulator - w/ inc regulator:
OEM : 27700-57060 : ±290$
OEM remanufactured for Toyota by Denso 27700-5760-84 : ±80$
.... I face the same problem with my ex-BJ60 and my actual BJ70. I know what i'm talking about. trust me.
Don't rebuilt the alternator... just change the regulator. It's not so hard to do by yourself. Go get the 3B factory service manual in the charging system section.
