  We present a complete analysis of the neutral fermion sector of
supersymmetric E_6-inspired low energy models containing an extra SU(2),
concentrating on the Alternate Left-Right and Inert models. We show that the
R-parity conserving scenario always exhibits a large Dirac mass for \nu_L with
maximal mixing with an isosinglet neutrino, and that R-parity violating
scenarios do not change the picture other than allowing further mixing with
another isosinglet. In order to recover Standard Model phenomenology,
additional assumptions in the form of discrete symmetries and/or new
interactions are needed. We introduce and investigate Discrete Symmetry method
and Higher Dimensional Operators as mechanisms for solving the neutrino mass
and mixing problems in these models.
