Small breaks in the conductive threads of the grid of the working element can be eliminated 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 OK, but part of the heater is not working. Proceed to the next step of verification.
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 a 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 central part of each of the grating strands (see accompanying illustration).
5. A reading of 5 ÷ 6 V indicates that the thread is in good condition. A zero reading indicates a break between the center of the thread and the positive side of the element. Double reading (10÷12 V) occurs when there is a break between the center of the thread and the negative side of the element. Check each of the lattice threads one by one.
6. If there are no breaks, connect the negative probe to the chassis ground and repeat the test - the readings should not change, otherwise there is a violation of the grid grounding quality.
7. To localize the break, press the negative probe of the voltmeter to the negative terminal of the heating element grid. With a positive probe wrapped in foil, begin to probe the conductive threads of the grid, moving from the side of the power supply to the ground. At the break point, the reading should drop from a few volts to zero (see accompanying illustration).
Refurbishment
1. Restoring the integrity of the conductive threads is carried out using a special Dupont type repair kit No. 4817. The basis of the kit is a conductive epoxy paste supplied with a hardener.
2. Turn off the heater and allow the element to cool for a few minutes before refurbishing the work element grille.
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 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 about 20 mm on the edges of the intact 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.