This International Standard specifies a test method for passenger car (as defined in ISO 3833) rear-window defrosting systems, when these are fitted. It does not specify reference areas or levels of performance, since at the time it was prepared there was insufficient data available. NOTE — It may be possible to carry out tests of a similar nature on windscreen and rear-window simultaneously. The test method is intended to apply to types of power-driven vehicles which do not differ from one another in respect of the following essential features which affect defrosting performance: a) shape, size and surface characteristics of the rear-window; b) characteristics of each system designated by the vehicle manufacturer as contributing to the defrosting of the rear-window.