Buzz
Cars might be small in terms of visible features, but they hide a lot of curious details. From the meaning of strange dashboard symbols to the purpose of the ‘A’ button, not to mention the mystery behind grab handles above car doors, there’s much to uncover.
One such enigma involves the horizontal lines that appear across rear windshields. But why are they there? Are they on every car? Do they even have a specific name?
So, why do cars come equipped with lines across their rear windows? Here's the explanation behind this feature.
Motor Biscuit explains that the lines on a car’s rear windshield are actually secondary defrosters. These thin metal and resin wires embedded in the glass carry an electric current and generate heat when activated, helping clear frost or condensation quickly.
Unlike the vehicle’s main heating system, which uses warm air from vents to clear the front windshield, the secondary defrosters on the rear windshield don't rely on air. Instead, the heating elements are integrated directly into the glass, allowing for faster defrosting.
Why don't all windows have defroster lines?
It might seem ideal not to have to wait for the car to defrost or scrape off ice and snow from side windows during winter. However, secondary defrosters are not present on front or side windows due to two main reasons: visibility and practicality.
Though the lines on the rear windshield may obscure part of your view, most driving is forward-facing. Having lines on the windows you look through the most might cause distractions.
The design of the front windshield plays a key role: It is typically made with multiple layers to prevent glass shards in the event of a crash. While adding secondary defrosters is possible, it's significantly more difficult compared to the thinner rear glass.
However, manufacturers have attempted it. The 1986 Ford Taurus featured a heated front windshield, marketed as Insta-Clear by Ford, utilizing a wire conduction system. Several luxury brands, such as Porsche, Jaguar, and Rolls-Royce, include heated front windows, employing either fine conductive wire or a conductive film within the glass to minimize or eliminate visibility issues caused by the wires used in rear windows.
The demand for heated glass is largely driven by colder climates, which may explain why car manufacturers hesitate to adopt it due to its cost and uncertain benefits. For consumers, the issue of dealing with a failed heating element is also a concern, as it would typically require purchasing a brand-new windshield.
Heated front windshields are more commonly found in Europe, while in the United States, they are mainly reserved for luxury vehicles. Unless a more affordable solution is developed, drivers will likely continue scraping ice off their cars for the foreseeable future.
