At equatorial point,due to dipole electric field is
$E_e=\frac{1}{4\pi {\epsilon }_0}\frac{p}{r^3}$
But electric potential due to dipole at a point on the equiorial line is 
(directed from +q to -q) and $V_e=0$.

$V=\frac{Q}{4\pi {\epsilon }_{0}r}\Rightarrow V_e=\frac{+q}{4\pi {\epsilon }_0}-\frac{q}{4\pi {\epsilon }_0}=0$