  In this paper, minimal supersymmetric AdS$_3$ solutions on $G_2$-orientifolds
of type IIA and IIB supergravity are studied. These are obtained by techniques
of the bispinor formalism. A straightforward argument is derived against
AdS$_3$ solutions in massless type IIA string theory on such $G_2$-backgrounds.
Furthermore, it is shown that some of the AdS$_3$ solutions in massive type IIA
do admit a separation of scales, whereas the same cannot be said for the type
IIB vacua. Finally, a formula for the 3d superpotential in the bispinor
language is given that is valid for both type IIA and type IIB configurations.
It is shown that the supersymmetry conditions of this superpotential lead back
to the bispinor equations.
