The semi-active damper idea is not new. Many previous researchers showed that a semi-active damper and an on-off type semi-active damper can each bring about almost die equivalent suspension performance as that of an active suspension system. In this work, a self-operating on-off type semi-active damper idea is devised. The advantage of the self-operating on-off type semi-active damper over the conventional semi-active damper or on-off type semi-active damper is its mechanical simplicity. The self-operating semi-active damper does not need any sensors and logic circuits for on-off control motion and brings about an identical suspension performance. In order to prove the practical applicability of the damper, two prototype dampers are designed, built and tested. As a result, the tested prototype damper shows very good agreement not only with the peak damping forces, but also with the timely self-operating on-off valve motion.