Control of an electrically heated pre-heating device for cold-starting internal combustion engines

A method for heating up the intake air of an internal combustion engine during a preglow phase or a start-up phase with at least one electrically heatable heating element in an intake line of the internal combustion engine, heating power being controlled by a control unit as a function of operating data of the internal combustion engine, comprising:

• supplying the heating element with full current during the preglow phase until the heating element reaches its reference temperature,
• beginning a post-heating phase, in which the heating element is kept at a constant temperature by a relatively low power, after the reference temperature has been reached and until the start-up phase,
• switching the heating element off in a first time period during the start-up phase, and
• switching the heating element on again in a second time period during the start-up phase in which the speed of the internal combustion engine is raised to the starting speed.