A method for converting a blow molding machine with a plurality of rotatingly movable molds heated to a heat-set operating temperature, due to mold change, having at least one simulated work cycle carried out in the blow molding machine with molds left empty, and a cooling medium then simultaneously supplied to all mold cavities from the outside so as to cool the molds in comparison with the heat-set operating temperature. In a machine control the blow molding machine has a program routine for performing at least one simulated work cycle with empty molds and at a reduced rotational speed of the molds with external supply of a cooling medium into the molds.