Expert advice: Defrosting cars – all you need to know

Defrosting cars

Iced up car windows are all too familiar at this time of year

Defrosting cars is something we all have to do at some point in the year. Although it sounds simple and should be relatively straightforward there are still some dos and don’ts. Here are my top tips to ensure you defrost your car and get going, even in the toughest conditions.

How to defrost your car

The most effective way of defrosting cars’ windows is still with a scraper. It’s always best to use one that’s designed for the job. I know people who swear by credit cards and even old CD cases. The danger with these is they may scratch the screen. A proper ice scraper will allow you to shift the ice quickly and effectively. You can also get de-icer sprays. These are an easy way of doing the job but they’re expensive.

How not to de-ice your car

Don’t try to de-ice your windows by running your windscreen wipers. All you’ll do is cause excessive wear to the blades. And it’ll all be in vain because it won’t shift the ice anyway. Don’t pour boiling water over your windscreen either. It will certainly be very effective at melting the ice. But it’s also a very effective way of causing your screen to crack. If you’ve got a small chip or some damage that you may not have noticed, the boiling water will get into it and the sudden expansion will turn that tiny chip into a rapidly spreading crack. Finally, I read a hack somewhere that involved getting an old plant sprayer and putting a salt water mix in it. I’m sure this works a treat but salt is highly corrosive so your paintwork won’t thank you for it.

Defrosting cars

Spray de-icers are very effective but they can be pricey

De-ice all the windows

You wouldn’t believe how many people we see driving around looking through portholes scraped in the ice. Hazards come at us from all angles when we’re on the road. It’s important that we can see all around us, so make sure you clear the ice from the side windows as well as the entire windscreen.

Defrosting cars: Watch out there’s a thief about

There have been some high-profile cases recently where drivers have started their engines in the road or on the drive. They’ve then gone back inside for a nice hot drink. In the meantime an opportunist has come along, jumped in and driven off. Of course just because the car is there with the keys in and the engine running doesn’t make what the thief does right. But it does make the car fair game. What’s more, insurers are within their rights not to pay out because they can argue the drivers haven’t taken sufficient care of their possessions.

If it’s really cold…

When the thermometer really does drop below zero, locks can freeze up. One way of thawing them is to boil a kettle, leave it to cool for 10 minutes, then pour it over the lock. Parking brakes can stick on too. This is because moisture freezes on the surface of the metal components in the mechanism housed inside the back wheels. If you can, pour a kettle of hot water through the spokes of your rear wheels to free it.

And if you drive a diesel

Diesel engines can be difficult to start in the winter because diesel is more susceptible to cold weather than petrol. Diesel relies on the fuel being compressed in the cylinder and the heat this generates to ignite. But when an engine is very cold, the engine absorbs that heat, making it difficult for the fuel to burn. To get over this, diesels have things called glow plugs. These ignite the fuel even when conditions are freezing cold.

Dashboard warning light for diesel glow plugs or engine management systemFirst thing’s first: when you turn the ignition on, an orange light with a symbol like a curly wire will appear on the dash (left). This light indicates that the glow plugs are heating up. When the light goes out, they’re hot enough to ignite the fuel. When you turn the key the engine should fire easily.

If starting the engine is still difficult in the cold, it might be sensible to take the car in for a service. A new fuel filter may well cure the problem.

self-driving carsNick Reid is a fellow of the Institute of the Motor Industry and head of transformation at Green Flag

15 comments on “Expert advice: Defrosting cars – all you need to know

  1. Zoop January 2, 2017 7:01 am

    You can buy isopropyl alcohol (IPA) very cheaply and use a mist spray, or simply buy your IPA in such a container. See ebay for examples.
    This when sprayed lightly on even thick ice, softens it rapidly and makes sraping easy.
    It is the primary ingredient in de-icer and has the advantages of doing little or no harm to your car plus removes grease and similar films from inside and outside surfaces.
    1ltr food grade (99.999%) IPA @ <£7 lasts me over a year and I use it to clean my spectacles, glass surfaces and other workshop uses.
    It is flammable and slightly toxic so google it before you start splashing it everywhere so you know what you are doing.
    Don't confuse IPA with India Pale Ale, which doesn't work that well as de-icer. :-\

  2. Myk January 25, 2017 6:40 pm

    You didnt mention that leaving your car running whilst unattended (called quitting) is illegal in the UK.
    It’s also illegal to leave it idling for extended periods even if you’re in it!

  3. Mr E Tilley February 5, 2017 11:18 am

    agreed that pouring a kettle of BOILING water on the glass is a no no, but warm water in the kettle from the sink tap, about 15-20 C is very effective and does no damage. Also use a good quantity when it is really cold and it warms to screen enough to prevent it re freezing when you drive out of the gate.

  4. Barry M February 6, 2017 2:27 pm

    I agree with E Tilley above, a good quantity of warm water has worked for me for years to defrost the car with the advantage that the glass does not freeze on the inside as soon as your breath hits it.

  5. Amy February 7, 2017 1:57 pm

    As stated warm water (not hot) is a great option for clearing hard ice. I then roll my windows down and wipe the windscreen to rid the excess and stop re-freezing. Care should be taken not to use wipers when frozen solid – fuses and motors often go bust that way! Most new diesels don’t have glow plugs, but I know from experience (13 yr old car) that a slower starting engine can be due to some plugs being dead. 2 of 4 of mine went, and when they were replaced my engine started easier in the cold. A new filter won’t really address that issue. Best have plugs checked as if they break when still inside, they are a nightmare to replace.

    • Paul February 9, 2017 4:03 pm

      The water method I have used for years, tepid and just warm water is all you need. If its just a light frost frost even water from the cold tap will work. one addition is that with the ice gone, turn on the wipers to dry the screen otherwise the water could freeze if you don’t drive off strait away.

  6. frogwatcher February 9, 2017 12:31 pm

    Why not just put an electric fan heater in the car for a few minutes? It has the advantage of not just de-icing and de-misting the windows but also warms the whole interior of the car beautifully. The flex feeds through the front door which is held safe on a chain into the vestibule. No keys needed in the car.

  7. Graham smith February 9, 2017 3:28 pm

    all good practical advice. my tip to prevent icing on the inside is to remove as much moisture as possible. first switch of your heater at approximately half a mile prior to your destination ( you do not want warm moist air to condense on the cold glass ). Secondly put an inch or two of Cat Litter in a used ice cream tub and place on the dash board. after say a week pop tub in the micro wave to renew. magic.

  8. Bladerunner February 9, 2017 3:38 pm

    Question what is lpa

  9. PR February 11, 2017 5:16 pm

    I have used COLD water for years. Provided it is not lower than -5 then it is quick and effective.
    2 old 2l milk bottles will so the screen and front side windows.
    1. Start the car and put on the heater blowing onto the scene.
    2. Pour 2l of water over the windscreen and then put on the wipers
    3. Use the the other 2l to do the side windows and any part of the screen that still has ice on it.

  10. Emark February 12, 2017 11:22 am

    De-icing all the windows is also compliant with the law as full all round vision is required by the driver prior to moving away, it’s a legal requirement so insurance could also use this as a point of reference along with the police.

  11. Stuart February 12, 2017 11:36 am

    Put a hot water bottle in the car just before you go to bed

  12. Peter February 13, 2017 7:26 am

    Warm water, what temperature is that? Use water straight from your COLD tap which is probably around 10 degrees C, thats plenty “warm” enough. A garden watering can 11/2 gallons I’ve found is plenty and yes it will warm the screen nicely and reduce the internal fogging. Use a window cleaners squeegee or wipers to remove excess water. I have a shelf of ‘spray de-icers’ which have frozen on the screen. Scrapers are a definite NO NO!! Idling an engine to warm up is also a NO NO as oil pressure maybe reduced and not reach all parts quickly. Drive ‘easy’ for first mile or two, don’t floor it from the word go.

  13. Mike@southpole February 16, 2017 4:31 pm

    If you’re retired, go back to bed with a cuppa and waith for Spring to arrive (usually in March)

  14. Paul December 1, 2017 6:18 pm

    Always used warm water from a watering can for the last 40 years. Never cracked a windscreen yet. All done in 1 minute. Not sure what all the fuss is about

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