In a method for detecting a disconnection in the charge line between a generator and an electric battery in a motor vehicle, the generator output voltage is measured and is evaluated at least with respect to the ripple voltage. The fly wheel of the oval-shaped mechanism simultaneously drives the driving arms and the swing handle, and the slidable bars are pivoted onto the assembling portion of the swing handle and rest on the shaft of the fly wheel such that the movements of the slidable bars are not limited by the driving arms and longer the travel stroke of the fly wheel. The key body is slidably mounted to the base plate between the two elastic elements.