How to Repair a Faulty Rear Window Defroster

  • 1-3 hours
  • Beginner
  • 35-75
What You'll Need
Warm Water
Rubbing alcohol
Glass cleaner
Masking tape
Conductive paint
Small paintbrush

The rear window defroster of your car plays an important role, both for practical and safety purposes. If you experience problems with it, you will definitely need to repair it. Here are some basic guidelines which will enable you to carry out the repair job yourself. The problem behind a fault in a rear window defroster could either be due to a break in the lines of the grid, or of an electrical nature.

Step 1: Inspecting

Use a voltmeter to discern where the break in the grid of defroster lines lies. The voltmeter will read the voltage at each point. Move it along the grid. The grid is the horizontal metallic strip found at the edge of your car's rear window. Once it shows a lower reading, you will be shown the point where the problem lies. You might find more than one break. In that case you will have to repeat the steps outlined here at each point.

Step 2: Switch Off

Switch off the defroster before starting work. It is important to remember to do this for safety purposes.

Step 3: Cleaning

Clean the area where the repair needs to be done. Remove dirt by spraying some glass cleaner and wiping the area. Then, use a mixture of warm water and rubbing alcohol and gently scrub the area with a dampened cloth. This step is important because if the area is not properly cleaned, you will not achieve a satisfactory result in the end. By cleaning it you will be removing dust, dirt and other residues, and this will enable proper adhesion of the conductive paint you will be applying afterwards.

Step 4: Prepare the Area

Once the area has been cleaned and wiped dry, stick masking tape on either side of the grid.

Step 5: Applying the Conductive Paint

Apply the conductive paint between the masking tape strips. Make sure to coat well so as to ensure there are no breaks in the grid. Make sure to allow the paint to dry well and remove masking tape before using the defroster.

Step 6: Other Repairs of an Electrical Nature

If you suspect that there are problems of an electrical nature, besides a break in the grid, you will also have to know how to repair them. This is, in fact, fairly simple. First, check the fuse, as it might not be strong enough to supply adequate current from the car battery to the defroster. The voltmeter can help you determine the strength. If you deem it to be insufficient, you will have to replace the fuse with a new, stronger one. Also, make sure to check that the wiring terminals of the defroster grid are properly attached. If you discover them dislodged, make sure to adjust them accordingly so as to enable a proper connection. If you suspect there are problems in the wiring, you may need to replace the switch.