Defroster is not working inspection—explained

If you notice that your front or rear defroster is no longer melting snow and ice properly, you’ll want to get it inspected. The front and rear defrosters are designed differently, so the inspection process will depend on which defroster is acting up. A mechanic can take a look at each component to figure out the source of the problem and make the necessary repairs.
Your front defroster uses a combination of hot and dry air —the hot air melts ice and snow, while the dry air prevents fog and humidity from subsequently building up on your front windshield.
Your rear defroster is made up of tiny wires laid out horizontally across your rear windshield—these electric wires are heated by warm currents flowing through them, melting ice and snow on the rear windshield.

How to get a defroster inspection

When you realize that your defroster isn’t working properly, bring your car to a mechanic. Explain the problem, and the mechanic will inspect the possible causes.

Front defroster

If your front defroster isn’t working, the mechanic will look out for each one of these possible culprits:
  • Stuck buttons: Sometimes, all it takes to unstick defroster buttons is to gently manipulate them, which may solve the problem.
  • Clogged fresh air intake: The fresh air intake is at the base of the windshield and can become clogged with snow, leaves, or other debris.
  • Vent issues: Vacuuming your interior vents may solve a clog, but if not, the issue could be deeper inside the ventilation system.
  • Low antifreeze: Antifreeze moves through your vehicle’s heater core to keep it running—if you are out of antifreeze, the heater core won’t work and you’ll have no way to defrost the windshield.
  • Thermostat issues: If your vehicle’s thermostat is broken, this can prevent your car from warming up, meaning the defroster won’t have any air to melt ice and snow.
  • Faulty heater core: This mini radiator is vital to your car’s heating system working properly—contaminated antifreeze can clog the core; hoses can break or come loose; control valves can get stuck; the heater core can cease to work due to damage or age.
  • Defective blower: The blower propels hot air through the cabin and your car’s defroster units—a blown fuse and broken blower speed controller will hamper the defroster.

Rear defroster

If your rear defroster isn’t working as designed, the mechanic will inspect for each of the following issues:
  • Heating grid damage: Any damage or contact with your rear windshield can damage the grid wires, which will be a problem when you try to defrost the rear window.
  • Busted tabs: On each side of the rear heating grid are two tabs, one positive and the other to the ground—if either is damaged, the defroster won’t work.
  • Age: Your defroster’s grid wires can lose conductivity as the vehicle ages, and damage from the sun’s rays, objects making contact with the wires, or harsh cleaning chemicals can further hamper their effectiveness.
  • Window tinting: Tinting may increase your privacy, but your grid wires can be damaged by the tinting as it bonds to those wires.

How important is it to inspect your defrosters?

Properly working defrosters are essential to your visibility on the road, especially if you live in an area with harsh winters. If your vision is obstructed, you could put yourself or other drivers at risk. If you notice any issues with your front or rear defrosters, take your vehicle to a trusted and qualified mechanic as soon as possible.

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