Contents: Examination ⇊ Restorative repair ⇊
The working element of the rear window heater is a horizontal grid of conductive threads glued to the inner surface of the glass. Power is supplied to the heater through a 30 A fuse from the power distribution unit located in the engine compartment of the car. The heater is turned on using a switch located on the instrument panel of the car. On Integra models, the continuous operation time of the heater is limited by a timer included in the built-in control unit.
Minor breaks in the conductive threads of the working element grille can be repaired without dismantling the rear window.
Examination
1. Turn on the ignition and rear window defroster.
2. Press the positive probe of the voltmeter to the positive terminal of the heating element grid, press the negative probe to the negative terminal. The device should register battery voltage, otherwise check the condition of the fuse, switch and connecting wiring. If the voltage is normal, but part of the heater does not work. Proceed to the next step of testing.
3. In order to measure the voltage during the tests described below, wrap the positive probe of the voltmeter with metal foil, which can then be easily pressed with your finger directly to the conductive thread of the heating element grid (see accompanying illustration). Connect the negative probe of the meter to the negative terminal of the grid.
4. Measure the voltage in the center of each of the grid threads (see accompanying illustration).
5. A reading of 5-6 V indicates that the filament is in good condition. A zero reading indicates a break between the center of the filament and the positive side of the element. A reading that is twice as high (10-12 V) indicates a break between the center of the filament and the negative side of the element. Check each of the grid filaments in turn.
6. If there are no breaks, connect the negative probe to the chassis ground and repeat the check - the readings should not change, otherwise there is a violation of the quality of the grid grounding.
7. To locate the break, press the negative probe of the voltmeter to the negative terminal of the heating element grid. Using the positive probe wrapped in foil, begin to probe the conductive filaments of the grid, moving from the power supply side to the ground. At the break point, the reading of the device should drop from several volts to zero (see accompanying illustration).
Restorative repair
1. Restoration of the integrity of conductive threads is carried out using a special repair kit such as Dupont No.4817. The basis of the kit is conductive epoxy paste, supplied complete with a hardener.
2. Before starting any repair work on the working element grille, turn off the heater and allow the element to cool for a few minutes.
3. Lightly clean the damaged area of the thread with felt, then wipe it thoroughly with alcohol.
4. Apply two strips of tape along the area of the thread to be repaired.
5. Thoroughly mix the epoxy paste with the hardener.
6. Apply the resulting composition to the damaged area (with an overlap of approximately 20 mm on the edges of the undamaged thread) (see accompanying illustration).
7. The final polymerization of the compound occurs after 24 hours, after which the protective tape strips can be removed from the glass.