Defroster Grid Breaks
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 crack can cause the defroster to fail. Be sure to have the work area well lighted. If the break is not obvious after close visual inspection, use a volt meter or 12 volt lamp to help locate the damage. Turn on the defroster and touch one meter lead to each of the wide vertical bars along the sides of the defroster. The reading should be between 12 and 14 volts. If the volt meter shows a negative reading, reverse the leads.

Now take readings at various places along the horizontal lines of the grid to isolate the break. When you pass over the break, the reading will change sharply. If you do not have a volt meter you can use the 2400 Frost Fighter Test Lamp. A really good way to identify broken or "worn out" lines is to switch on the defroster in cold/damp or humid weather to identify which lines are working and which are broken or damaged.  

Once a break or breaks in the defroster grid has been located, it’s time to consider how to repair the problem. The 2100 Frost Fighter Grid Repair Kit is designed to repair grid damage. Use the grid kit to precisely mask off the damaged area of the defroster. There may be more than one break in the grid so locate all the damage before proceeding.

After the damaged areas have been located and masked, apply the repair material using the small cap brush supplied. Frost Fighter grid repair kits use a highly conductive silver polymer repair compound. This polymer bonds aggressively to glass and provides maximum electrical conductivity. The material dries to the touch in 10 minutes and is usable in thirty minutes. The conductor is color matched to the reddish brown colors used in automotive defrosters for nearly invisible repairs.

Removing the masking tape after the polymer dries leaves a uniform highly conductive defroster repair. It is important that repairs be done at normal room temperatures and that the conductor be allowed to fully cure before activating the defroster. Repairs can be completed even more quickly by applying heat to the repair. A lamp or hair dryer can be used to speed curing. Care must be used not to damage the glass or any tinting that may be on the window. 