Some years ago, we studied the conditions under which we can formulate a consistent theory of a massive spin-1 field (in the adjoint representation of $SU(N)$ ) coupled to gauge bosons. It was found that, when we impose consistency with unitarity, an accidental $Z_2$ symmetry appears. We use this fact to extend the Standard Model by adding a massive spin-1 field in the adjoint representation of $SU(2)_L$ . The neutral component of this new vector triplet becomes lighter than the charged ones due to radiative corrections and it is stable because of the accidental $Z_2$ symmetry, making it a Dark Matter candidate. In this talk
we will comment about the constrains on this model coming from colliders and cosmological observations. We will also discuss what happen when we extend the Standard Model by putting the new vector in the fundamental representation of  $SU(2)_L$  rather than in the adjoint representation.