Caution: wrap thin foil around the voltmeter probe. Use your finger to press the foil against the conductor and move it along the conductor to locate the open circuit.
1. Turn on the rear window defroster. Use a voltmeter to measure the voltage at the middle of each heater filament. If the voltage is approximately 6 V, the heating element is good.
2. If the voltage is 12V, there is an open between the center point and the positive terminal.
3. If the voltage is 0V, there is an open between the center point and the negative terminal.
4. To find the location of the break, slowly move the probe towards the possible break. At the breaking point, there will be a sharp change in voltage.
5. Using an ohmmeter, measure the resistance between the terminal and the center of the heating filament, as well as between the same terminal and the center of an adjacent filament. A broken heating element will have twice the resistance of a good element.
1. Heating element without breakage;
2. The central point of the thread with a break;
3. Terminal (+). Voltmeter shows twice the voltage