rear defog assistance needed

[Eugene]

The defog lines are broken and I was wondering what can be done to repair them. I know that there are fix kits but has anybody used one before? Results?
If that isn't possible is there anywhere I can take it to be repaired?
TIA gang,
Eugene

[Mark D.]

The defog lines are broken and I was wondering what can be done to repair them. I know that there are fix kits but has anybody used one before? Results?
If that isn't possible is there anywhere I can take it to be repaired?
TIA gang,
Eugene
STOLEN FROM THE ROADFLY BMW BOARD
Good Luck Eugene, your gonna need it....


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Modern automotive rear window defroster are sophisticated surface heaters. The grid pattern of thin brown horizontal lines are made from a silver ceramic conductor which is first silk screened to the inside of the rear window and then baked at very high temperatures. These grids are hooked up to a high amperage circuit to provide rapid heating. The average defroster grid heats up to approximately 85°F and is very effective in clearing fog and ice from the rear window. Although effective, rear window defroster grids are vulnerable to damage and with back window glass costing hundreds of dollars to replace, repairing a damaged defroster grid makes a lot of sense.

Trouble Shooting

Typically there are two ways rear window defrosters fail. First, the thin horizontal lines can be broken or scratched away from the rear glass causing the defroster to only partially defrost the rear window. Defrosters can also fail when the main power tabs are knocked off of the defroster’s vertical side bars, causing a total defroster failure.

Defroster Grid Repairs

If the defroster clears only part of the rear window, it’s usually a sign of a broken horizontal grid line. The first step in repairing this type of damage is to locate the break by visual inspection. The smallest break or cracked trace can cause the defroster to fail. Be sure to have the area well lighted while you complete your inspection. If the break is not obvious after close visual inspection, use a volt meter to help locate the damage.

Once a break or breaks in the defroster grid have been located, it’s time to consider how to repair the problem. There are several relatively inexpensive repair kits available to do the job. These kits use a conductive coating that, once painted over the break, repairs the defroster grid. A leading kit is the Frost Fighter Grid Repair Kit available on line at www.frostfighter.com. There may be more than one break in the grid so be sure to locate and mask all the damage before proceeding.

Defroster Tab Repairs

When the electric defroster grid does not work at all, small breaks in the horizontal grid are not the problem. In this case the more likely cause of a total defroster grid failure is a separated main power tab. These critical tabs connect the defroster grid with the vehicle’s high amperage defroster circuit and are located on each of the defroster grid’s vertical side bars These all important main power tabs can be knocked off of the defroster causing total defroster failure. Look for dangling wires near the sides of the defroster as a sure indication of this problem. Once this problem has been identified the challenge becomes reliably reattaching the separated tabs without damaging the back glass or the existing defroster.

The best way to repair these separated tabs is to use an electrically conductive glue to reattach them back to the defroster. Most tab repair kits use a highly conductive silver filled epoxy that cures quickly and bonds aggressively to glass forming both the electrical and structural connection in one simple operation. These adhesives are available on line at www.frostfighter.com.

Other Problems

If the problem isn’t a break in the defroster grid, or a separated main power tab, then the problem is in the defroster circuit. Begin by trying to turn the defroster system on. If you hear the system’s relay click and the monitoring lamp is on, you know you have current. This can be checked by testing to determine if power is reaching the two main power tabs on the defroster. These tabs should have around 12Vdc. If the there is no power to the grid then carefully check the switch and the wiring.

By using these tips and through careful trouble shooting, damaged rear window defrosters can be easily and economically repaired, saving hundreds of dollars in the process.