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How to Stop Your Car Windows From Fogging Up Inside

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JP993 is a self-confessed car and motorcycle addict, having saved thousands over the years working on and maintaining his vehicles himself.

With the weather getting colder and wetter, the hindrance of getting in our cars first thing in the morning with frozen fogged-up windows is upon us. This isn't great when you're late for work. So what can you do to stop your car windows from fogging up?

First things first, clear the frost on the outside of the windscreen, if any. This will increase the temperature slightly of your screen.

If you do this job with the engine running, great, but I have to emphasize that you should not turn your car's heating on as soon as you start the car. The heat you get from your heaters is drawn from the engine's cooling system. (Confused yet?) If you turn on your fans straight away, you'll be taking away the little heat the car has generated and actually be cooling the engine. Don't turn your heaters on for a good five or ten minutes; after that, you can blast the heaters and clear your screen a lot quicker than if you had them running from startup.

OK, this step may not sort out a steamed windscreen if there's a problem, but it may get you on your way quicker.

If your car steams up no matter what you do, then here are a few things you should do to prevent excess moisture building up and to maybe eliminate some causes of that.

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  • If you are always in a hurry and wipe the windscreen on the inside with a mitt or tissue, this could be one of your problems. Doing this makes the windscreen dirty and oily, making it easier for the moisture to build up, so no sooner have you wiped it than it steams up again. Try to avoid wiping your windscreen.
  • Get some good window cleaner, like 5-star rated Invisible Glass Cleaner. Rain-X does a windscreen repellent for the outside which I can not rate high enough; this stuff is excellent. It dramatically increases visibility on those journeys when your windows wiper can't keep up. By cleaning your windows, you should dramatically reduce the moisture buildup.
My favourite windscreen cleaner

My favourite windscreen cleaner

  • If the heaters inside your car never get hot, then your problem may be that your car's thermostat has gone. The job of the thermostat is to stop water circulating around the engine until it reaches a certain temperature, thus making the engine warm up quicker. This is not just a benefit for your heaters, but it lets your car's oil reach its operating temperature quickly. So if your heaters just never get hot, then your car may need a new thermostat. These are very cheap to buy and pretty simple to change; any mobile mechanic should be to change your thermostat in under an hour easily. (To heat your car, you can also buy a 12-volt heater that plugs straight into your car's cigarette lighter socket and gives instant heat.)
  • Also feel your carpets for water or dampness, if you suffer from your car's windows fogging up on rainy days even more than on the usual cold, damp days, Check your footwell carpets. If they are excessively wet, then you may have a problem with your windscreen (a crack or poor seal) or a leak in your heater matrix. You can tell if your heater matrix is leaking because if it is, you will lose water in the header tank. A cracked windscreen can be changed on your insurance if you are full comp.

The best thing to do is clean your windscreen with a good-quality auto window cleaner, like Invisible glass cleaner, and see if this reduces moisture build-up. You will always get fogged-up windows; older cars will suffer more from this problem, due to them having less of everything. If you're having problems with heat, then you need to look more on the mechanical side of things; and if you have water in the car, you'll never get rid of the fogging until you have caught the culprit.

In short, here are seven things you can do remove or reduce fogging up:

  1. Clean all your windows properly on the inside.
  2. Remove frost from your windscreen quickly with a liquid de-icer.
  3. Do not use a sponge or cloth to wipe it off.
  4. Give yourself plenty of time to warm your engine up so your heaters can remove the condensation.
  5. Open your windows slightly, if your clothes are wet, to let the moisture escape. Put wet coats in the back or in the boot, if possible, to put the moisture at the back of the car.
  6. Check your footwells for puddles.
  7. Replace a cracked or chipped windscreen.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

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