A rear window defroster is an incredibly useful feature, especially in cold and icy climates. It helps clear frost, fog, and ice from your back window quickly so you can see clearly out of your rearview mirror. However, like most things in a car, a rear defroster can eventually fail or become damaged. When this happens, many wonder if repairing a rear window defroster is possible or if the entire rear window needs to be replaced. Luckily, in many cases, rear window defrosters can be repaired rather than fully replaced.
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How Does a Rear Window Defroster Work?
A rear window defroster is made up of a grid of very thin wires affixed to the inside surface of the rear window. The wires are powered by your vehicle’s electrical system and when turned on, they heat up to help melt ice on the window. Most rear defrosters turn off automatically after 10-15 minutes so they don’t overheat.
The defroster grid wires are very fragile and over time can become damaged from sun exposure, extreme temperatures, debris hitting the window, and normal wear and tear. If the wires become broken, the circuit is disrupted and the defroster will fail to work properly across parts or all of the window.
Can You Repair a Broken Defroster Grid?
If you notice your rear defroster is no longer working fully, the issue is likely some broken wires in the defroster grid. The good news is that these wires can often be repaired instead of necessitating full rear window replacement. Here are some key factors in determining if a rear defroster grid can be repaired:
Accessing the Defroster Wires
To repair broken defroster wires, you first need to gain access to the wires on the inside of the rear window glass. On many vehicles, the rear window is not designed to be fully removed, so a professional auto glass technician will need to carefully cut into the window seal to reach the wires around the edges.
Type of Damage
If there are just one or a couple breaks in the wire grid, these can usually be repaired by splicing in new wire. However, if there is significant corrosion and extensive broken wires, the defroster may be too far damaged for repair attempts to be worth it.
Repairing the Wires
Once accessible, a technician will check for breaks in the wire grid pattern. Any severed wires will need to be spliced and connected. The technician may also apply an epoxy-like sealant over wire repair areas to ensure the grid remains intact.
Resealing the Window
After the grid wires are repaired, the window seal that was cut will need to be replaced with new rubber window sealant. A professional can ensure this is sealed correctly so moisture cannot enter and cause new damage.
Rear Window Defroster Repair Cost
The cost to repair a rear window defroster will depend on the technician’s hourly rate, the extent of the damage, and the car make and model. On average, expect to pay *between $200 and $400* for a rear window defroster repair job. Here are some examples of typical defroster repair costs:
| Repair Type | Average Cost |
|---|---|
| Minor grid wire splicing repair | $200 – $250 |
| Complete grid wire replacement | $300 – $400 |
Replacing an entire rear window could cost $500 or more, so repairing the defroster grid is often considerably less expensive.
DIY Rear Defroster Repair
While it’s recommended to have a professional auto glass technician conduct rear defroster repairs, some vehicle owners may attempt DIY repairs:
Removing the Window
This can be very difficult and risky on modern unibody vehicles. Only attempt if you have experience removing bonded-in auto glass.
Accessing the Defroster Wires
Use a sharp razor to cut into the window rubber seal just enough to reach the wire terminals near the edges. Take care not to damage the wires.
Repairing Broken Sections
Use a splicer crimp tool to reconnect any severed wires. Seal with waterproof heat shrink tubing.
Resealing the Window
Apply fresh automotive-grade window sealant around the access cuts and edge. Roll up the windows to press the glass back into place.
DIY repairs can be done for under $50 in materials but have greater risk of sealing issues if not done properly.
Other Rear Window Defroster Repairs
Beyond the defroster grid wires, there are some other repairs related to the rear defroster system:
Defroster Switch
If the switch to turn on the defroster is damaged, this just needs to be replaced with a new OEM part, typically easily accessible in the dash.
Fuse
Sometimes a defroster stops working due to a blown fuse for the defroster circuit. Easy fix by replacing the fuse.
Relay
An electrical relay that engages the defroster may fail over time. The relay will need to be replaced.
When to Replace Instead of Repair
In some situations, it will not make sense to repair a rear defroster and full glass replacement will be the better option:
– Extensive damage to large sections of defroster wires
– Other damage like cracks in the glass outside of just the defroster grid
– An older vehicle where the cost of repair approaches the cost of full replacement
– DIY repairs attempted unsuccessfully
If the damage is beyond just simple wire splicing, replacement may end up being easier, cheaper, and more effective.
Preventing Rear Defroster Damage
To maximize the longevity of your rear defroster system, follow these tips:
– Never use scrapers, squeegees, or abrasive pads to clear ice on the rear window as they can easily damage the wires
– Turn off the defroster once the window is mostly clear of ice/fog rather than leaving it on unnecessarily
– Fix any cracks or chips in the rear window as soon as possible to prevent further cracking
– If wires start to look visibly corroded or damaged, have a technician inspect and repair as needed
Conclusion
In many cases, a damaged rear window defroster grid can be repaired rather than requiring full glass replacement. An experienced auto glass technician can splice broken wires and reseal access cuts for significantly less cost than a new rear window. DIY repairs are possible but much more difficult and risky. Make sure to address any defroster issues promptly to avoid more extensive damage that may necessitate complete replacement. With proper maintenance and timely repairs when needed, a rear window defroster can last the life of most vehicles.