Here's What Those Lines On Your Car's Rear Windshield Are For

The average automobile is jam-packed with mysterious design decisions, things that make little-to-no sense at a casual glance from anyone but a professional automotive mechanic or engineer. It's easy to assume the incidental elements of your car are just for stylistic purposes, and certainly, some of them are. Things like hood ornaments don't have much practical application, for example. However, many of these odd details actually do serve important roles in your car's safe operation, some of which you may have been making regular use of without even realizing.

One good example of this is the small, yet distinctive lines you see across a rear windshield. It's easy to dismiss this as an aesthetic touch, as it does have a certain stylish punctuation to it. Whether you think the lines look cool or not, though, they are very much there for a reason, and it's an especially important one: keeping your rear windshield clear during inclement weather conditions.

Those lines across your car's rear windshield aren't just stylish racing stripes or the remnants of peeled window tint, they're actually a vital component of your car's window defrosting system. If you've ever taken a drive when it's especially frosty or foggy out and needed to get the ice and fog off your rear view, you've already made use of this nifty system.

The lines on the rear windshield aren't just drawn on with paint — they're actually wires made up of electrically-conductive materials like metal or resin. The wires are either directly attached to the surface of the rear windshield via an adhesive, or they're sealed directly into the windshield itself while it's being manufactured, kind of like sandwiched glass. When you engage the defrosting system on your car's dashboard, a slight electrical pulse is sent into these wires, causing them to subtly heat up. It's not so hot as to affect the atmosphere inside the car, but just enough to loosen up any ice or fog stuck to the windshield. It's a very simple, yet effective system for keeping frost from obscuring your rear view.

You may be wondering, if those windshield wires are so important, why aren't they present on the front windshield, and why do some cars not have them? The answer to both of those questions is potentially one and the same: they do have them, you just can't see them.

For your front windshield, heating wires are less necessary because defrosting comes from your AC vents. When you engage the frontal defroster, they just shoot warm air up into the windshield, heating it from the inside out and melting frost in the same way as the wires. That said, some newer models of car actually do have heating wires embedded in the front windshield. However, these wires are much thinner and finer than the ones in the back. After all, if you had thick lines covering your front windshield, that'd be a major hazard while out driving on the road. These same fine wires may be used on some rear windshields as well. If it looks like your rear windshield doesn't have lines, they may just be too fine for you to make out at a casual glance.