Method to operate a glow plug for a vehicle heating device

To operate the glow plug in a vehicle heating system, on starting up the heating, the glow plug is set for working at a nominal heating power (L). During the initial heating interval (I1) of the start phase a lower nominal heating power (L1) is set than the power used in the following heating interval (I2). During the third interval (I3) of the start-up, a lower nominal power (L3) is used than in the second interval. The excitation of the glow plug finishes at the end of the third interval.