>NB.: Does anyone has diagrams (electrical and mechanical) for this
auxiliary that could be scanned and emailed to >me?

Welcome Michel

http://www.type2.com/bartnik/ba6art.htm ---- good tech article on the BA6
which is what I think the '84 has

http://www.conservatory.com/vw/manuals_nyx/  --- manual for the BA4 ---
possibly of some use.........

Cheers,
Doug