This invention provides apparatus for projecting light, for a motor vehicle, comprising: a light source having a discharge bulb, a high tension module, and a bulb base for making the connection between the bulb and the high tension module, a counterpart comprising a reflector and a lamp holder, with the said lamp holder holding the bulb in front of the reflector, and a fastening system for fixing the light source on the counterpart and situated at least partly around the lamp holder, the fastening system comprising: a rotatable rigid sleeve, and an electrically conductive flexible annular ring situated inside the rigid sleeve and having tongues in electrical and/or mechanical contact with the light source.The invention also provides a method for fitting the said apparatus.