The heated rear window (defogger) on my 1988 Volvo 740GL Saloon has stopped working. There are 12 volts at the connection on the window (just by the left hand rear seat belt anchor point) and the earth at the other side is OK. I have measured the resistance of the window with the 12v and earth wires attached and it is around 10k ohm but without the wires attached it is around 100k ohm. These values are far too high to let any useful current pass. There is also a high resistance between the 12v or earth connectors and the vehicle body. There are no cut outs or timers in the circuit. I guess the window has had. Has any one else had this problem or know why it should have happened. It will be too expensive to replace the window so I was thinking of fitting a 150/200watt heater to blow on the rear window. Has anyone any views on this fix.