The invention describes a method for operating glow plugs in a diesel engine that comprises a housing and a heater element projecting beyond that housing which interacts with an engine control unit and a glow plug control unit which, following a preheating phase, controls the electric power supplied to the glow plugs in dependence on an input received from the engine control unit. According to the invention it is provided that the engine control unit determines a value representative of a temperature that is to be reached at the heater element and the engine control unit transmits that value as target value to the glow plug control unit which converts that target value using an algorithm stored in the glow plug control unit and taking into account the characteristic values stored in the glow plug control unit.