Automatic belt tensioners are used in serpentine belt drive systems in many automotive front end accessory drive (FEAD) applications. The dynamic characteristics of the tensioner must be well defined in order to accurately model the entire belt drive system for system simulation studies. In order to determine required tensioner performance parameters, six different configurations of a production unit were tested over a wide range of frequencies at two different amplitudes of the arm travel. Data was recorded to define the total torque generated by the tensioner as a result of the known input motion to which the arm was subjected.A mathematical model was developed which accurately represents the measured experimental data over the frequency range and amplitude range tested. This paper will describe the test procedure, measured tensioner performance, and the correlation with the mathematical model for the production tensioner only.