What is the little window on the back of a truck for?

There are so many things we take for granted when it comes to our cars. Thousands of little details are overlooked every day. Sometimes, you may see something on your car and not really know why it’s there. If you’ve ever wondered what the little lines that run across your back window are, let’s fill you in!

The lines are wires built into the window to quickly defrost it

According to Miracle Auto Glass Center, the lines that run through your rear window are actually wires that heat up to defrost it. The official name of these lines on the rear window of your car is secondary defrosters.

Though many cars have vents that defrost the front windshield as well as the front windows, you’ll find that most vehicles don’t have vents to defrost the rear. Sure, the window will eventually defrost or de-ice due to ambient air temperatures rising in the vehicle with your heater on. However, the secondary defrosters can defrost your rear window in a matter of minutes without relying at all on the vehicle’s heater.

The secondary defrosters are usually a grid of wires that are all connected to one power source. So, once you activate them, all of them begin heating up immediately. However, unlike the heating system that provides warm air to the vents in most cars, the secondary defrosters do not rely on engine and coolant temperatures to heat up. So, even if the rest of your car is not warmed up yet, the secondary defrosters will still do their job.

Having properly functioning secondary defrosters can be a lifesaver on cold winter mornings. Think about it; how many times have you been running late and didn’t have time to wait for your car to warm up before you needed to leave? Sure, you still have to scrape most of the windows on a frigid morning. However, the secondary defrosters can do their thing while you clear everything else and save you a bit of time.

Moreover, they can provide much-needed rear-window visibility.

Why don’t front windows and front windshields have secondary defrosters?

Naturally, one might think that it would make sense to use this technology throughout all the glass on the vehicle. That way, the secondary defrosters could quickly clear all of your windows without having to exert your precious energy with a window scraper. However, there are a couple of reasons why that’s not a great idea.

Most obviously is visibility. While rear-window visibility is definitely important, having the secondary defroster lines in your rear-view mirror isn’t all that distracting. Think of the last time you had a rock chip or big bug on your windshield, though. That can be quite distracting. Now, imagine having two dozen black lines running the length of your windshield and side windows.

Additionally, front windshields use two-pane laminated glass with a layer of plastic between the glass. This way, if the windshield brakes, it doesn’t shatter into a million pieces all over the cabin and its occupants. Attempting to insert secondary defrosters into windshield glass would require a lot of re-engineering.

However, some companies are actively developing invisible electric glass heaters for this very application. Though there are currently no vehicles with this technology on the market, it may not be far off.

Additionally, some vehicles do have wires in the windshield at the base to warm frozen windshield wipers.

So, next time you’re with someone who’s curious about what the lines do that run through your back window, you can tell them all about secondary defrosters!

Also called a valance window or vent glass, a quarter glass window is a side-facing window on a vehicle that is significantly smaller than the standard passenger windows and often serves as an extension of the passenger window either above the rear wheel or next to the side-view mirrors.

These small-paneled windows can sometimes open to allow air to enter and ventilate the car. This style of window first came into popularity in the 1950s when they were standard on virtually every vehicle. During this time period, almost all quarter glass windows operated on a manual tilt mechanism, allowing the glass panel to pivot outward, letting air enter the vehicle. This type of vent glass was extremely popular before the emergence of air conditioning in automobiles because it allowed the driver and passengers in the front seat to direct airflow into the vehicle to cool off.

It wasn’t until years later when fuel efficiency became a concern and air conditioning was more common that these windows were modified to their current, non-tilt design. Nowadays many sedans and other vehicles are equipped with stationary quarter glass windows extending from either the front or rear side windows. In fact, some vehicles are equipped with both. Still today, many common models of minivans utilize tilt technology in their third-row quarter glass windows.

Why is it There?

While the purpose of tilting quarter glass had its roots in ventilation in early vehicles, stationary quarter glass windows are still relatively commonplace. Since the need for ventilation to cool a vehicle is no longer a common concern, many people wonder why we still utilize these windows at all. The answer is quarter glass windows greatly enhance the driver's visibility of the surrounding area. In the rear of the vehicle, the presence of a quarter glass window can allow the driver to view an area that would typically be a “blind spot.” Furthermore, when these small windows appear on the front of a vehicle, they allow the driver to increase the visibility of the side-view mirrors and the front of the vehicle.

Replacing Quarter Glass

More often than not, quarter glass panels are made from the same tempered glass that your vehicle’s windshield and passenger windows are made of. For that reason, if there is any damage to the quarter glass, it should be addressed immediately.

There are three primary ways that quarter glass can break.

• The glass itself can break, resulting in a full replacement.
• The weather stripping that holds the glass in place can become damaged or weakened causing leaking and other damage.
• The window-opening mechanism can break if the windows are not stationary windows.

Sometimes, vehicle owners are under the impression that since the quarter glass is the smallest piece of glass on their vehicle, it is the least expensive to replace. While in some cases that can be true, the cost of a repair varies depending on the make and model of the vehicle at hand. Realistically, quarter glass replacement can range from $100-1,000 depending on the vehicle and the piece of glass broken. If the quarter glass is functional and not stationary, the replacement will be much more expensive.

Next time you need a quarter glass replacement, look no further than Smiley’s Glass in Richmond, Virginia. We offer the safest and finest services when it comes to vehicle glass repair or replacement. You can rest assured that we use only quality, manufacturer approved products as prescribed by the Auto Glass Safety Council’s AGRSS program. For more information on our expert auto glass repair or replacement services, you can contact us by dialing 804-320-7172.

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