  We test in a simplified 5-dimensional model with SU(3) gauge symmetry, the
evolution equations of the gauge couplings of a model containing bulk fields,
gauge fields and one pair of fermions. In this model we assume that the fermion
doublet and two singlet fields are located at fixed points of the
extra-dimension compactified on an $S^{1}/Z_{2}$ orbifold. The gauge coupling
evolution is derived at one-loop in 5-dimensions, for the gauge group $G =
SU(3)$, and used to test the impact on lower energy observables, in particular
the Weinberg angle. The gauge bosons and the Higgs field arise from the gauge
bosons in 5 dimensions, as in a gauge-Higgs model. The model is used as a
testing ground as it is not a complete and realistic model for the electroweak
interactions.
