How Does a Defroster Work?

Summary. A car defroster clears condensation and removes frost, snow, and ice from a vehicle's windshield and windows. By default, defrosters work using heated air or heat grids to prevent condensation from forming on the vehicle's glass windows and windshield and obstructing the driver's view .

Have you ever wondered how a rear defogger, also known as a rear defroster, works in a car? It’s a simple yet interesting process that we’re going to explain to you in this blog post.

When your rear windshield gets frosted or fogged, or when there’s snow or ice on it, you can activate your rear defogger to either melt off the snow and ice or defog the window. But how does it work?

If you take a closer look at the rear windshield, you’ll notice that there are lines on the inside that carry an electrical current. When you turn on the rear defroster button, it sends a small electrical current through these lines to heat them up. This reaction causes the windshield to heat up enough to either defog or defrost it.

There are no ducts on the rear of the car, unlike the front, so the defroster works differently. It’s the reaction of the electricity on the windshield that causes the heat, not the electricity itself.

The rear defogger button is usually located somewhere on the dashboard, and when you push it, it illuminates. Electrical current then flows through the lines on the rear windshield, heating it up enough to melt any ice or snow and defog the window.

It’s important to note that in most cars, the rear defogger or defroster automatically shuts off after a certain amount of time to prevent the rear windshield from shattering. Leaving it on for an extended period can cause this to happen.

In conclusion, the rear defogger is a simple yet effective way to defrost or defog the rear windshield of a car. It uses electricity to create a reaction among the rear window, which heats it up enough to serve its purpose. So, the next time you activate your rear defogger, you’ll know how it works!


Do I use hot or cold air to defrost windows?
For a quick fix: According to Road and Track, this is the fastest way to defog your windshield: First, turn the heat on its maximum setting because hot air can hold more moisture. Then, turn the AC on, which will pull the moisture from the air as it passes over the cooling coils.
How does defrosting windshield work?
Windshield defrosters blow air from the heating and ventilation system onto the windshield through vents at the forward edge of the dashboard. Most vehicles have a setting for directing all air to the windshield for maximum defrosting or splitting the air between the windshield and floor level.
Does the defroster use the air conditioner?
The big surprise about defrosters is the system that drives it… the air conditioner. It is your air conditioner that helps to get the moisture out of the air (and off the windshield). When you turn the defrost on, it's your air conditioner that kicks in to help get all that moisture out.
What happens if you leave your defroster on?
If you leave it on while the engine is not running, then you will quickly flatten the battery. Other than that, it will do no harm leaving it on. It will of course cause a small increase in fuel consumption.