Posted by Karl on January 15, 2001 at 13:03:50:
In Reply to: rear defrost barely works posted by Eugene on January 14, 2001 at 21:52:50:
As Michael pointed out, the defroster is a parallel grid. Ii is common for individual traces to be broken, and that line in the window will not heat. But regardless of whether all the traces are working or some or all are broken, you'll still get 12V across the whole grid.
Troubleshoot individual traces by connecting your multimeter to the ground side, then run the voltmeter probe along each trace. In a good trace, voltage will decrease gradually from 12 to 0 as you move along the trace.
In a broken trace, the voltage will remain 12V as you move along the trace, then drop abruptly to 0 as you cross the break.
Once you find breaks in the grid, they can be repaired with a kit commonly available at auto shops--or use a pen for drawing conductive traces on a circuit board from an electronic shop.
Not a difficult job.