Mechanical vibrations of a solar module mounting rack cause oscillations in the orientation of the module towards the sun. The resulting intensity oscillations of the incident light generate an a.c. current at the module's terminals. We have investigated this effect in the laboratory by means of a vibration table and outdoors, where wind forces induce vibrations to the mounting rack. Although the collected results are specific and restricted to our experimental set up and the regional environmental situation we deduce that vibration induced current transients and oscillations of a solar module's output most often will be the dominant origin of distortion in the low frequency regime. (C) 2011 Published by Elsevier Ltd.