What is the Job of a Window Defroster?
There are two different types of window defrosters: front windshield defrosters and rear window defrosters. The front windshield defroster is designed to blow large volume of air on the windshield with the goal of dissipating condensation that has built up on the inside of a windshield. When the weather is cool, droplets of water can form on a vehicle's windows. Condensation on the inside of the windshield occurs because the air outside is colder than the temperature inside the car. When the temperatures become even colder, the condensation turns to frost or ice, which must be scraped away by hand or thawed by the defroster.
How Front and Rear Window Defrosters Work:
In simple terms, the front defroster works by circulation of air, while the rear defroster is electrically charged. The front defroster has vents on the dashboard that face the windshield and front windows. The fan and blower motor that operate the heating and air conditioning will also circulate air through these vents to defrost the windows.
The process of operating the front defroster is unique to your vehicle. In general, to activate the front defroster, all you have to do is make sure the vents are open, turn on the fan and turn the setting to defrost and set the temperature to the desired setting. In most cases, warmer air blowing on the inside of the window will expedite this, but on the first engine start of the day, it will take time to create heat.
The rear defroster is electric for most vehicles. The rear window will have thin lines running across the window. These lines are electrical fibres embedded in the glass that heat up as they are activated. This defroster has its own button that you access when you want to defrost the rear window. You will notice the condensation or ice dissipating first along the lines until the entire window is clear.
How the Defrosters are activated:
Front defrosters work best when the air blowing onto the window is warm. However, it takes time for heat to build up in the engine and activate the heater core. When the coolant reaches a certain temperature, it will open the thermostat. Hot water will move through the core of the heater while the blower fan pushes the warm air through the vents of the defroster to warm up the windows. The condensation or ice will begin to dissipate as the window reaches the desired temperature. If the heater is not working, the front defroster will have difficulty working correctly.