How to Defrost a Frozen Windscreen Fast (and Safely)

Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent

The fastest safe method, step by step

On a typical frosty Kent morning this takes about five minutes if you do it in the right order.

1. Start the engine and set the controls. Air direction to the windscreen, fan on maximum, temperature to hot, air conditioning on (it dries the air) and recirculation off. Switch on the heated rear screen and heated front screen if you have one.
2. Spray de-icer on the outside. Work from the top so it runs down over the glass. Give thick ice a minute to soften.
3. Scrape with a plastic scraper. Use the straight edge at a low angle and push the slush off the glass. Do the side windows and mirrors too.
4. Clear the lights and number plates. Frosted headlights and indicators are easy to forget.
5. Check the wipers are free before you use them. Frozen blades tear easily, and a wiper motor straining against ice can blow a fuse or strip its linkage.

Stay with the car while it runs. Leaving it ticking over unattended on the drive is a common way cars get stolen on frosty mornings, and insurers may refuse a claim if the keys were in it.

De-icer vs scraper: which works better?

They do different jobs, so most drivers in East Kent end up using both.

• Scraper only: fine for a light white frost. Cheap, quick and nothing to run out of. Use plastic, never metal, and keep the edge clean so grit does not scratch the glass.
• De-icer only: good on thin frost, slower on thick ice. It also helps stop the screen refreezing as you set off.
• Both: the best option after a hard freeze, such as the clear, still nights we get inland around Aylesham, Barham and the Elham Valley.

Avoid bank cards, CDs and anything with a sharp corner. They break, scratch or leave patches of ice on the line of sight.

What not to do

• No hot or boiling water. The sudden temperature change can crack the screen, especially if there is already a stone chip. The water also refreezes on the glass and on your driveway.
• Do not drive off peering through a small hole. It is dangerous and you can be stopped for it.
• Do not run the wipers on a frozen screen. Free them first.
• Do not set off with snow on the roof. It slides down over the screen the first time you brake.

Ice on the inside of the glass

If the screen freezes inside, the car has too much moisture in the cabin. Common causes are wet floor mats, a blocked pollen filter, a door seal or scuttle drain letting water in, or a heater matrix leak. Coastal damp in Deal, Dover and Folkestone makes it worse. Our guide on a windscreen misting up inside covers how to track it down, and a fresh cabin pollen filter often makes a clear difference to how fast the glass clears.

How to stop it freezing in the first place

• Use a windscreen cover or an old blanket held in by the doors on nights below zero.
• Park facing east if you can, so the morning sun reaches the screen first.
• Keep the screenwash topped up with a proper winter mix rated well below freezing.
• Replace split or streaky wiper blades before the cold sets in.
• Keep the inside of the glass clean. A greasy film holds condensation and freezes faster.

For a full list of jobs before the cold weather, see our winter car checklist for Kent drivers.

How we can help

If your screen keeps misting or freezing on the inside, your demister is weak, or the heater blows cold, we can come to your home or workplace and find out why. We check the pollen filter, heater and blower operation, coolant level and thermostat, and look for water getting into the cabin. Labour is £30 to £50 per hour depending on the job, and you get a quote before any work starts. Send your reg and postcode on WhatsApp 07563 350335 or use our contact page.

Frequently asked questions

Can I use hot water to defrost my windscreen?

No. Hot or boiling water on cold glass can crack it, and the water often refreezes on the screen and the road. Use de-icer, a proper scraper and the car's demister instead.

Is de-icer or a scraper better?

Both together is best. Spray de-icer to soften thick ice, then clear it with a plastic scraper. On a light frost a scraper alone is usually enough.

Can I leave my car running to defrost while I go back inside?

It is not a good idea. Leaving the engine running unattended is a theft risk that insurers may not cover, and Highway Code rule 123 says you must not leave a vehicle's engine running unnecessarily while it is stationary on a public road.

Why does my windscreen freeze on the inside?

Moisture inside the car condenses on the cold glass and freezes overnight. Wet mats, a blocked pollen filter or a water leak are the usual causes, so dry the cabin out and get any leak found.

Sources

• The Highway Code: driving in adverse weather conditions (rules 226 to 237)
• The Highway Code: general rules for all drivers (rules 103 to 158)