A heated windscreen has electrically operated wire conductors spaced throughout the glass, which, when activated, melt ice and de-mist the car window for optimum viewing. As of 2011, most cars come equipped from the factory with a heated rear windscreen, and many new models also have front-heated windscreens as an optional extra, depending on the make and model. Before continuing, consult your vehicle's manual, locate the windscreen's fuse and replace it. If this does not solve the problem, your windscreen heating grid may be damaged. With the correct tools, this repair can be done at home.
Clean the entire windscreen inside and out with a soft cloth and window cleaner to remove any dust and built-up dirt. Purchase a defroster repair kit from a local auto parts store.
Turn on the windscreen heating system. Using a volt meter, place the probes of the meter on the horizontal grid line at both ends of each line and take the reading on the volt meter (usually 12 volts). Move one probe, it does not matter which, to the center of the line. If it reads 6 volts, the break is not between the two probes, if it reads 12, the break is between where the probes are now. Continue moving the probes until you straddle the location that has full 12 voltage spanning it; that's where the break is. Perform this on each horizontal line of the grid if more than one line has not been working.
Use a grease pencil on the outside of the glass to mark where the damage is. Clean the area with rubbing alcohol to remove any oily residue. Place the masking tape horizontally on each side of the break, making sure the repair is only as wide as the break.
Using the defroster repair kit purchased, shake the small vial of conductive paint thoroughly and brush the paint over the break. Wait a minute and add a second coat. Leave for 2 minutes and then remove the masking tape.
