1. Turn on the rear window heating. Connect a voltmeter to one end of the heating network and to the center of the glass. The voltage should be 6V.
2. If the voltmeter shows 12 V, then the network break is between the voltmeter contacts.
3. If the voltmeter shows no voltage, then the network break is located behind the voltmeter contacts.
4. To accurately locate the break, move the foil slowly. The break is at the point where the voltmeter changes readings.
5. Perform this procedure for each network line.