Method for heating a glow plug

The method involves providing temporal distribution of effective voltage that is generated by pulse width modulation (PWM) and is applied for heating at a glow plug. An annealing program is stored in a controller and is provided for a glow plug, where characteristics e.g. electric characteristics such as electric resistance, capacity and inductivity, of the glow plug correspond with production tolerances. Difference of a value of the characteristics from a nominal value is determined. The annealing program is adjusted as function of the determined difference. An independent claim is also included for a glow plug controller comprising a sensor.