How to Use Car Defrosters: A Guide to Mastering the Defrost Button

Download Article

The quickest ways to defog your windows and melt ice

Co-authored by Duston Maynes and Annie Johnston

Last Updated: June 5, 2024 Fact Checked

Download Article

What does the defrost button look like?

|

Using the Defrost Button

|

Do you defrost with hot or cold air?

|

How long does it take?

|

Defrost Best Practices

|

Video

|

Warnings

When the windows in your car are fogged up, the defrost setting is crucial. We're here to explain what the defrost button looks like, where to find it, and how to use it so that you can get rid of fog and ice quickly. Read on for simple steps on mastering the defrost button in your car.

Locating the Defroster Button

The defrost button has a symbol that looks like a curved window with three upward arrows going through the center. The front windshield defroster button is usually curved, while the button for the rear window defroster is rectangular.

Section 1 of 5:

What does the defrost button look like?

Download Article

The front defroster button in your car can usually be found on the dashboard. It looks like a curved window with three upward-pointing arrows in the center.
In most vehicles, the rear defroster button is located fairly close to the front defroster on the dashboard. It looks quite similar, but the symbol is usually rectangular (instead of curved) and has three arrows.

Section 2 of 5:

How to Use the Defrost Button in a Car

Download Article

Simply press the button and make sure that it’s on by checking to see if it’s lit up. Press the rear defroster button, too, if your back window is obstructed by condensation or ice.
2
Set the heat and fan speed on high. When the air inside your car is humid, the cool surface of the glass causes that moisture to condense into tiny water droplets on the windows and windshield. Heat is what combats this, so turn the heater and the fan to their maximum settings.^{[1]
X
Research source}
- Directing this warm air flow at the windshield and front windows will help evaporate the excess moisture on the glass.
3
Turn on the A/C. Turning on the air conditioning (A/C) after cranking up the heater may seem a bit backward, but it actually activates the condenser in the A/C system, which aids in drying the interior air faster by pulling out moisture. While you can defrost your car without using the A/C, using the A/C together with the heater is the quickest way to effectively defog and defrost.^{[2]
X
Research source}
- If you’re simply defogging your car and not defrosting it, you can stop at this step and wait for the condensation to clear from your windshield. If defrosting, continue to the next step.
To quickly dry the saturated air inside your car, allow fresh, dry winter air to enter the inside. Cold winter air holds less moisture, so introducing it will help remove excess humidity from the interior more efficiently.^{[3]
X
Research source}

Section 3 of 5:

Do you defrost with hot or cold air?

Download Article

Defrosting with hot air is most efficient. Defrosting your car is faster if you run the engine and turn on the heater. This warms the interior and windows, accelerating the defrosting process.^{[4]
X
Research source}
- Although it is recommended to turn on your A/C in conjunction with your defroster, keep the heat as high as it goes rather than turning the blend door to cold.

Section 4 of 5:

How long does it take to defrost the windows?

Download Article

A car usually takes anywhere from 5-20 minutes to defrost. This depends on many different factors, such as the weather, the temperature, the humidity, the amount of frost, and even your own car's functionality. Generally, though, if it's raining or snowing outside, always allot yourself ~20 minutes of defrost time to play it safe and avoid running late.^{[5]
X
Research source}
- The front defroster is controlled through the vehicle's heating and ventilation system. Windshield defrosters direct air from the HVAC system onto the windshield through vents at the front of the dashboard. Most vehicles offer a dedicated defrost mode that channels all airflow to the windshield for maximum defrosting.^{[6]
  X
  Research source}
- You can adjust the temperature and fan speed for the defroster. During winter, using the defrost mode with a high-temperature setting accomplishes two key functions: it defogs the windshield and melts frost/snow, making it easier to scrape the glass and preventing ice buildup while driving.^{[7]
  X
  Research source}
- Powered by electricity and operated by a dashboard switch, the rear defroster button sends an electrical current to a grid of thin wires visible on the inside of the glass, heating the rear window to defog and melt frost, snow, and ice.^{[8]
  X
  Research source}
- The rear defroster starts working immediately, but the front defroster requires more time to get going during cold weather. This is because the front defroster relies on the engine's warm coolant circulating through the heater core before it can blow warm air onto the windshield.^{[9]
  X
  Research source} Most rear defrosters run on a timer that automatically shuts them off after about 10 minutes.

Section 5 of 5:

Defrost Best Practices

Download Article

1
Use a deicing solution if there’s frost. To clear excessive snow and ice after the defroster button has already been running, use a store-bought deicer or make a homemade solution of ²⁄₃ cup (5.3 fl oz) of isopropyl or rubbing alcohol and ¹⁄₃ cup (2.7 fl oz) of cool water. Pour the mixture into a spray bottle.^{[10]
X
Research source}
- This solution will not freeze as rubbing alcohol has a freezing point of −138 °F (−94 °C) allowing you to easily spray away windshield ice and keep it in your car throughout the winter for convenience.
- Don't use hot water, which can crack your windshield.
Most of us have all been in a rush or running late while trying to get out the door, but it’s important to allow the defroster to sit and do its thing. Every car is different, but giving the defroster at least 5-20 minutes (depending on the weather, how cold it is, and how much snow and ice is on your window) to run will ensure that your windshield is clear enough to drive.^{[11]
X
Research source}
When your window is layered with dirt and grime, it’s harder for the defroster to work. By keeping your windshields clean often, you’re allowing the defroster’s performance to be up to par.^{[12]
X
Research source}
Obstructing the air vents with objects like air fresheners or accessories restricts airflow and diminishes defrosting efficiency. Maintaining clear, unobstructed vents is crucial for optimal system performance.^{[13]
X
Research source}
Park your car so the morning sun hits the windshield. The sun's warmth can help melt ice or frost, working in tandem with the car's defrost function.^{[14]
X
Research source}
If you have the heat turned all the way up but find that your defroster is not blowing hot air, there could be an issue with the system. Some common reasons for the defroster to be down are: lack of antifreeze; clogged vents; frayed wires; a blown fuse; malfunction buttons or knobs, or cracks in the window tint. Follow up with a mechanic to properly diagnose and fix the issue.^{[15]
X
Research source}

Expert Q&A

Search

Add New Question

Ask a Question

200 characters left

Include your email address to get a message when this question is answered.

Submit

Video

Tips

Submit a Tip

All tip submissions are carefully reviewed before being published

Name

Please provide your name and last initial

Submit

Thanks for submitting a tip for review!

Warnings

Never try to bypass using the defroster button by pouring hot water on the windshield or using external heat to melt ice. The drastic change in temperature can actually crack the glass. What’s more, hot water will eventually just freeze, causing a counteractive result. Always use a deicing solution instead of water or heat in conjunction with the defroster button.^{[16]
X
Research source}

Thanks
Helpful 0 Not Helpful 0