How to Repair a BMW Rear Window Defroster

If the grid in your BMW's rear window defroster breaks, and the connection fails, the defroster line containing the break will not work. The typical cost to replace the rear windshield in a BMW was more than $400 as of October 2010. You can do the job yourself for around $10.

Instructions

1

Use the voltmeter to find the break in the connection. Turn the defroster on and place the voltmeter probes on either side of the damaged grid. The voltmeter should read 12 volts. Move one probe toward the other one, checking every half-inch until the voltmeter reads 6 volts. This is the area of the grid that needs repair. Once you have found the break in the grid, switch off the defroster.

2

Wash the area around the break with a clean rag and rubbing alcohol. Be sure to get all the dirt and oil residue off the window and grid so the conductive paint will stick and give you a sound connection.

3

Apply masking tape to either side of the grid at the point of the break. Put the masking tape just on either side so that only the width of the grid is between the two pieces of tape.

4

Shake the conductive paint well and apply it to your taped area. Paint all along between the two pieces of tape so that you will be sure to fill any breaks in the grid.

5

Let the paint dry for 24 hours. Remove the two pieces of tape and discard them.