Crack detector and heating circuit for motor vehicle headlight light transmissive shield

A circuit arrangement for a motor vehicle headlight of a type including a reflector and/or a lens, a light source coupled to a voltage-source device, an enclosing light-transmissive shield, at least one electrically conducting heating element on or in the light-transmissive shield, a switching-on apparatus for the heating element;

• wherein, the heating element is electrically coupled with an analyzing apparatus, the analyzing apparatus includes a light-transmissive-shield-crack monitoring means for detecting cracks in the light-transmissive shield which comprises a current or voltage measuring device, the light source is a high pressure gas discharge lamp, the voltage-source device being a power supply of the high pressure gas discharge lamp, and the switching-on apparatus and the analyzing apparatus are parts of the power supply of the high pressure gas discharge lamp for controlling power provided by the power supply to the conducting heating element and the high pressure gas discharge lamp in response to measurements of the light-transmissive shield-crack monitoring means.