Contents: Examination ⇓ Repair ⇓
1. The rear window defroster consists of horizontal heating elements glued to the inside of the rear window. Voltage is supplied to the heater through a fuse installed in the distribution box located in the engine compartment. The heater is activated by a switch located on the instrument panel.
2. Minor damage to the heating elements can be repaired without removing the rear window.
Examination
3. Turn on the ignition, then turn on the rear window defroster.
4. Connect a voltmeter to the positive and negative terminals of the heater. If the voltmeter does not show battery voltage, check the fuse, switch, heater relay, and associated wiring. If voltage is present, but all (or some) of the heating elements do not work, try the following:.
5. When measuring voltage in the following tests, wrap the voltmeter probe with aluminum foil and press the foil with your finger to the heating element (figure 22.5). Connect the negative probe of the voltmeter to the negative terminal of the heater.
6. Measure the voltage at the center of each heating element (figure 22.6). If the voltage is 5-6 V, then the corresponding element is working properly (that is, it has no gaps). If the voltage is 0, then there is a break between the center of the corresponding element and the positive terminal of the heater. If the voltage is 1-12 V, then there is a break between the center of the element and the negative terminal of the heater. Check each heating element.
7. If all components are in good condition, connect the negative probe of the voltmeter to the vehicle ground. The voltmeter reading should remain the same. If the voltmeter reading changes, it is necessary to restore the heater's contact with the ground.
8. To find the open point in the heating element, connect the negative probe of the voltmeter to the negative terminal of the heater. Place the foil-wrapped positive probe of the voltmeter onto the heating element, starting at the positive terminal and moving toward the negative terminal. At the point where the voltage suddenly drops from a few volts to zero, there is a break (figure 22.8).
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Repair
9. To repair breaks, you can use a repair kit (for example, Dupont paste kit #4917, or similar). The kit contains a special conductive adhesive.
10. Before starting repairs, turn off the rear window defroster and let it cool for a few minutes.
11. Clean the area around the heating element with a fine wire brush, then wipe the area with methyl alcohol.
12. Apply adhesive tape around the area of the heating element to be repaired.
13. Thoroughly mix the epoxy adhesive from the repair kit according to the manufacturer's instructions.
14. Apply glue to the break point and 2 cm of the heating element on each side of the break point (figure 22.14).
15. Allow the mixture to dry for 24 hours, then remove the adhesive tape.