We report the observation of the Fermi energy controlled redirection of the ballistic electron flow in a three-terminal system based on a small (100 nm) triangular quantum dot defined in a two-dimensional electron gas (2DEG). Measurement shows strong large-scale sign-changing oscillations of the partial conductance coefficient difference G(21) - G(23) on the gate voltage in zero magnetic field. Simple formulas and numerical simulation show that the effect can be explained by quantum interference and is associated with weak asymmetry of the dot or inequality of the ports connecting the dot to the 2DEG reservoirs. The effect may be strengthened by a weak perpendicular magnetic field. We also consider an additional three-terminal system in which the direction of the electron flow can be controlled by the voltage on the scanning gate microscopy (SGM) tip.