have you got a multi meter?? if not about a fiver from maplins (electronics not holiday camp), disconnect the window element and measure on the ohms scale accros the window, should be about 5.5 ohm i think!! simpler test if your screwdriver is one of those light up if you tock both end types, touch one end of the window with the driver and the other with your finger! if it lights up the elemnt is fine!! good luck!