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11 Jun 2018
Maria McCarthy Maria McCarthy

How to stop condensation in your car


Here's how you can fight back against the damp misting up your windows. 


Quick fixes to get rid of condensation

  • Wash your car to get rid of dirt particles that attract moisture.

  • Get rid of any damp items like coats and towels.

  • Fill a pair of tights with cat litter and leave in your car - this will help absorb excess moisture.

  • Air out your car by leaving the windows open for a few hours (when safe to do so).

  • Switch on your blower and A/C, and wipe down your windows thoroughly. 

It's bad enough having to live with the relentless dampness of the outside world without having to cope with it in our motors as well.

But many of us have to deal with condensation misting up, or in some cases streaming down, our car windows. So what's the solution?

What causes condensation in cars?

Condensation happens when there's a difference between the temperature and moisture levels inside and outside the car.

The car is a closed environment in which dampness and heat can build up.

When this moisture meets the cold windscreen it changes from invisible vapour into water droplets, which stick to the inside of your glass and impede vision.

Simply breathing inside a car is enough to start the process.

Making the matter worse

Leaving damp items such as jackets, umbrellas, car mats or dog towels also contribute to condensation.

Remember to always remove them when you leave the car. A blocked pollen filter, which cleans air entering the car, can be another possible cause.

But another likely reason is that the car has a leak somewhere that’s letting water in. It could be in a door, light or sunroof seal, or a leak in the heater matrix.

Identify the problem

Tracking down a leak can be challenging. A mechanic may be able to help as they'll know where particular models tend to let water in.

"Sorting out leaky cars is incredibly difficult," says Dave Richards, former editor of Classic Car Weekly and an experienced mechanic.

"It often involves stripping the car down completely. And even when you've found the leak it often can't be fixed easily or fixing it isn't economically viable.”

A costly fix

"For example, sorting out a leaking heater matrix can cost anything between £200 and £1,000, which generally isn't worth if for an older car.

"And unfortunately some cars start suffering from condensation at six or seven years of age. The older a car is, the more likely it is to develop this problem."

 Raining on car

How to fight back against condensation

But there are a number of steps you can take to at least alleviate it.

The first is to clean your windows thoroughly on the inside as well as on the outside.

Dirt particles on the inside of the windows give the moisture inside the cabin a surface to attach themselves to, and will make the condensation problem worse.

So use a cleaner designed for car windows and polish with a clean microfibre cloth or newspaper.

"It's also important to wash your car regularly," says Richards. "There are small drains as little as a few millimetres wide that are built into the body of the car, and if you don't clean it then they can become blocked.

"This build-up of detritus can then create dampness which contributes to the problem."

Absorb excess moisture

A very effective solution is to keep something in the car that will absorb moisture.

Putting cat litter in a pair of old tights and keeping it under the seat is a popular strategy. There are also various portable car dehumidifiers which you can place around the cabin.

Allowing the car to air whenever possible will also help. So if you're able to safely leave it with the windows open for a few hours, then do. If you've just got into your car and it's full of condensation, it's important to clear it before setting off so you have full visibility and can drive safely.

Wipe the windows down thoroughly with a clean cloth and switch on the heater blower, directing it at the windscreen.

Use your heater and demister

Instead of poring over your car's manual, use this quick run-down of the right settings to use when demisting your car:

  • Set your blowers to full, but keep the temperature cold at first. Point them at the windscreen and windows.

  • If you have A/C, switch it on. This will help keep the air dry.

  • If your car has heated windscreen settings, switch them on.

  • Gradually increase the temperature until the windows are clear.

First published 29 December 2017

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