Things You Should Know About Your Car’s Rear Window Heating


By  AIS Windshield Experts


Car Back Windshield: Things to Know About Read Window Heating

The rear window defogger or defroster is an incredibly useful feature in cars, especially during cold winter months when frost and fog can obstruct your rear view. Here are some key things you should know about how your car’s back windshield heating system works and how to use it effectively.

What is the Rear Window Defogger?

The rear window defogger, also known as the rear window defroster, is a heating element built into the rear glass of your car. It is designed to clear frost, fog, and condensation from your back windshield and rear side windows.

The defogger uses an electrical heating element made of thin metal strips overlayed inside the rear glass. When turned on, an electrical current passes through the metal strips, producing heat. This helps clear the glass of moisture so you can see clearly out the back.

How Does the Rear Defogger Work?

There are a couple of different systems that manufacturers use for activating the rear defogger:


In the timer-based system, the rear defogger is activated manually, typically by pressing a button or switch on your dashboard. Once turned on, it operates for a predetermined duration, usually around 10 to 15 minutes. This time limit is in place to prevent overheating or draining the vehicle's battery.

After the set time has elapsed, the timer-based rear defogger automatically turns off. If you require more defogging time, you must activate it again. This system allows you to control when the defogger operates, but it requires manual intervention.


The sensor-based system is more advanced and convenient. It relies on a temperature sensor that is usually mounted on the rear windshield. This sensor continuously monitors the temperature of the glass. When you activate the rear defogger in a sensor-based system, it doesn't operate for a fixed duration.

Instead, the sensor measures the temperature of the glass. Once the glass reaches an optimum temperature, the defogger turns off automatically. If the glass starts to fog up again, the sensor will detect the change and reactivate the defogger. This cycle continues as needed to maintain a clear rear windshield.

Tips for Using Your Rear Defogger

  • Activate the rear defogger at the first signs of fog or frost for best results. It works faster to clear light condensation versus heavy frost buildup.
  • Clear any mist from the rear windshield glass before turning on the defogger. This allows the heat to be transferred directly to the glass.
  • Make sure your rear wiper blades are in good condition. You may need to wipe away excess moisture as the fog clears.
  • Use the defogger in conjunction with your car’s air conditioning system. The A/C removes moisture from the air which aids the defogging process.
  • If you have sensor-based auto-shutoff, you can reactivate the defogger for additional clearing time.
  • Don't use scrapers or other tools to remove frost as you could damage the heating elements forcefully.

How Long Does the Rear Defogger Run?

Most rear defoggers will run for 10-15 minutes per activation cycle. This prevents the system from overheating and draining your car’s battery. Newer models with sensors may run continuously until the glass achieves optimum visibility.

The defogger will automatically turn back on if the temperature drops and condensation starts to form again. But for older timer-based systems, you’ll need to push the button again to restart the cycle if your back window fogs up after 15 minutes.


With a better understanding of how the back window defogger works, you can use this helpful feature more effectively. Just be sure to activate it at the first sign of fog or frost to maintain a clear rear view and drive safely.

Similar Post

Recent Post

Leave a comment

Your email address will not be published.

Toll-Free 1800-102-6364



iconInsurance Claim Enquiry Form icon
Request A Callback icon Find A Service Centreicon
icon1800-102-6364 icon9818866364 icon9599087715
  Offers & Deals

We use cookies to help you get the best possible experience of our site. By clicking 'Accept' you agree to our use of cookies.