Experiments were performed in vacuum to examine a modified Kaluza-Klein theory. Originally proposed by Mbelek and Lachieze-Rey, the 5D Kaluza-Klein- Ψtheory includes an external scalar field Ψto couple gravitational and electromagnetic fields and can be used to explain some misunderstood phenomena in physics. The theory predicts that a pendulum will experience detectable forces exceeding predictions from classical electromagnetism when interacting with a scalar field. In this experiment, a dielectric mirror is hung as a pendulum inside a vacuum chamber and its oscillations are examined with two laser interferometers. In proximity to the pendulum, different solenoids and toroids will induce magnetic fields that can also be shielded to a great extent using a Gauss chamber. The experiments were conducted in a vacuum chamber to allow the measurement of torsion angles as low as 0.1 arcsec above the noise, as well as 0.1 μm translations of the pendulum. The phenomenon observed differs from what was observed by Mbelek at ambient pressure in both magnitude and behavior. Dummy test results hint at the presence of convection effects to explain the pendulum's rotation, which was eliminated under higher vacuum and by placing a wall between the solenoid and pendulum. In the presence of stronger magnetic fields, the pendulum's translation was observed to agree with effects predicted by a consideration of diamagnetic effects.