Minor wire breaks can be repaired without removing the rear window from the vehicle.
Check the rear window defroster as follows:
To detect a break in the rear window defroster wire, turn on the ignition and the rear window defroster switch.
Connect one voltmeter probe to the positive terminal of the heater and the other to the ground terminal. If the voltmeter doesn't show voltage, check the fuse protecting the heater's electrical circuit. If voltage is applied to the heater terminals, perform the following checks.
Figure 15.44. Using a foil-wrapped voltmeter probe to locate a break in the rear window defroster wire
Connect one probe of the voltmeter to the ground of the car, and wrap the second probe with foil and move the foil along the heater conductor (see figure 15.44).
Figure 15.45. Using a voltmeter to locate a broken rear window defroster wire
Connect the voltmeter probe to the center of each rear window defroster wire. If the voltmeter shows a voltage of about 5.5 V, then the heater wire is good. If the voltmeter shows 0 V or 12 V, then there is a break in the heater wire (figure 15.45).
[The article was copied from the portal: toyotaman.ru]
Figure 15.46. Using a voltmeter to locate a break in the rear window defroster wire
To locate a break in the heater wire, connect one voltmeter probe to the positive terminal of the heater and move the other probe along the heater wire from the negative terminal of the heater. The point at which the voltage shown by the voltmeter drops from a few volts to zero will be the point where the heater wire breaks (figure 15.46).
Before repairing the heater, turn it on for a few minutes.
Repair the rear window defroster as follows:
Repair the gap using a special repair kit.
Strip the conductors on both sides of the conductor break and degrease them.
Use adhesive tape to seal the glass on both sides of the conductor at the point of its break.
Prepare the conductive adhesive compound from the repair kit.
Apply conductive adhesive to the broken and undamaged areas of each conductor at a distance of 18 mm.
Allow the conductive adhesive to dry for 24 hours, then remove the adhesive tape.