Radioactive ion beam facilities produce and extract isotopes and species of interest by employing a variety of target materials and ion sources. The forced electron beam induced arc discharge (FEBIAD) type plasma ion source * ** is the principal choice for volatile species such as noble gases and molecules and is also used in case surface or resonant laser ionization is insufficient. In its standard configuration, the electron energy is defined by the potential difference between the grounded cathode and the floated anode cavity. At CERN-ISOLDE, a special multi-voltage FEBIAD ion source has been prototyped, which isolates the electron acceleration grid from the main anode cavity body and decouples the cathode potential from the ground. This separation allows to tune the electron energy and potential shape within the anode, with the goal of studying properties such as ionization and dissociation energies of radioactive molecules. The influence of the multi-voltage assembly on the electron energy and electric field was characterized by simulations. Their results served as a reference for measurements on stable molecules, which were carried out at the ISOLDE Offline 2 separator.