A method for vehicle electrical system diagnosis by means of a regulator, which is configured to regulate the voltage supplied by a generator via a converter for a vehicle electrical system of a vehicle by outputting an output signal, wherein the method comprises the following steps: detecting an output signal by way of a control device, ascertaining an instantaneous power output at the vehicle electrical system on the basis of the detected output signal, and analyzing the ascertained power output for diagnosis of the vehicle electrical system and at least one electrical consumer which is connected to the vehicle electrical system.