  In a truly model-independent approach, we reexamine a minimal extension of
the Standard Model (SM) through the introduction of an additional $U(1)$
symmetry leading to a new neutral gauge boson ($Z'$), allowing its kinetic
mixing with the hypercharge gauge boson. An SM neutral scalar is used to
spontaneously break this extra symmetry leading to the mass of the $Z'$. Except
for three right-handed neutrinos no other fermions are added. We use the
current LHC Drell-Yan data to put model-independent constraints in the
parameter space of three quantities, namely, $M_{Z'}$, the $Z$-$Z'$ mixing
angle ($\alpha_z$) and the extra $U(1)$ effective gauge coupling ($g'_x$),
which absorb all model dependence. We impose additional constraints from
unitarity and low energy neutrino-electron scattering. However, limits
extracted from direct searches turn out to be most stringent. We obtain $M_{Z'}
> 4.4$ TeV and $|\alpha_z| < 0.001$ at $95\%$ C.L., when the strength of the
additional $U(1)$ gauge coupling is the same as that of the SM $SU(2)_L$.
