It is a cold December morning in Delhi. You start the car, pull out of the lane, and within a minute the glass in front of you turns milky white. You wipe it with your palm. It smears. You wipe again. Now it is worse, and there is a bus coming.
Windshield fogging is one of the most common winter driving problems in North India, and it is more dangerous than people treat it. At Citi Glass, we get plenty of calls every winter from drivers who think something is wrong with their glass. Usually nothing is. Sometimes something is. Here is how to tell, and how to clear the fog in seconds. A clean glass fogs less, so our guide on how to clean your car windshield without damaging it is worth a read, and so are our tips on preparing your windshield for seasonal changes.
Fog on glass is simply condensation. Air always carries some water vapour, and warm air carries more than cold air. When warm, moist air touches a cold surface, it cools down, cannot hold its moisture any more, and leaves it behind as thousands of tiny droplets.
That is the same reason a cold glass of water “sweats” in summer. Your windshield is just a very large cold glass.
This is the part most drivers never work out, and it changes what you should do.
Fog on the inside (winter). The glass is cold from the outside air. Inside the car, your breath, your body heat, wet shoes and damp clothes make the air warm and humid. That air hits the cold glass and fogs it from the inside.
Fog on the outside (monsoon and humid nights). Here it is the reverse. The AC makes the glass cold, and the hot, sticky air outside condenses on the outer surface.
Quick test: run the wipers once. If the fog clears, it was outside. If nothing changes, it is inside.
Follow these steps in order. It works on almost every car.
Within half a minute the glass should start clearing from the bottom up.
It is tempting, but your palm leaves a film of skin oil on the glass. That oily layer gives moisture something to cling to, so the glass fogs up faster and more unevenly next time. It also causes streaks and glare from oncoming headlights at night.
If you must wipe, keep a clean, dry microfibre cloth in the door pocket and use only that.
Keep the inside of the glass truly clean. This is the single biggest factor. Dust, smoke residue and the film released by dashboard plastics all attract moisture. Clean the inside with a proper glass cleaner every couple of weeks.
Keep moisture out of the cabin. Shake off umbrellas and wet shoes, do not leave damp cloths or wet mats inside, and dry the floor mats in the sun now and then.
Change the cabin air filter on time. A clogged filter cuts airflow, which makes the defogger weak and slow.
Use fresh air mode in winter. Long drives on recirculation build up humidity.
Try an anti-fog treatment. A good anti-fog spray on the inside of the glass helps a lot in peak winter.
Those thin horizontal lines on your rear windshield are heating elements. Press the rear defogger button, the rectangle icon with wavy arrows, and they warm the glass and clear it in a few minutes.
If some lines do not clear, the element is broken at that point, often from scraping the glass or peeling off a sticker. It can usually be fixed with a back glass repair.
Normal fog clears within a minute with the defogger on. Get the car checked if you notice any of these:
If fogging started soon after a windshield was replaced elsewhere, the sealing may not have been done properly.
Delhi winters bring fog and smog outside the car as well. A windshield that is scratched or pitted from years of dust and wiper wear scatters headlight beams and makes poor visibility even worse. If your glass looks hazy at night no matter how well you clean it, it may be worn. Our post on handling windshield scratches explains what can be polished and what cannot.
Good wipers matter too. Streaky blades make fog, drizzle and smog much harder to see through.
At Citi Glass, we check for leaking seals, moisture inside the glass and worn or damaged windshields, and we fix what actually needs fixing. From windshield repair to windshield replacement, we have Delhi drivers covered, and you can find good replacements on our wiper page.
Get ready for the season with a quick inspection. Contact Citi Glass today.
6/32, Gurudwara Rd, Block 6, WEA,
Karol Bagh, Delhi, 110005
