MOT Windscreen and Wiper Rules: Chips, Cracks and Washers
Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent
How the MOT looks at your windscreen
The MOT inspection manual divides the windscreen into areas. What matters is the swept area, the part of the glass your wipers clear, and within that zone A:
- Zone A is a strip 290 mm wide, centred on the middle of the steering wheel, within the swept area. It's roughly the part you look through when driving.
- The rest of the swept area is everything else the wipers cover.
| Area | Fail if damage or obstruction is larger than |
|---|---|
| Zone A | 10 mm |
| Rest of the swept area | 40 mm |
Damage outside the swept area doesn't fail on size alone, but a crack that spreads into the swept area can, and testers may note it as an advisory.
Chips, stars and cracks
Small stone chips are common on Kent roads, especially behind lorries on the A2 and M20 approaches to Dover. A chip that passes today can spread into a crack overnight in a hard frost, when the glass contracts and the heater then warms it quickly.
- Get chips repaired early. A specialist can often repair a small chip if it hasn't cracked.
- Avoid pouring hot water on a frozen screen. The shock can turn a chip into a crack.
- Don't slam doors with a fresh chip in cold weather.
- Check your insurance. Many policies include windscreen cover.
We don't repair or replace windscreens ourselves, but we can tell you during a pre-MOT check whether damage is likely to fail.
Want to pass your MOT first time?
We do pre-MOT checks and fix advisories at your home or work across East Kent.
WhatsApp for a free quote Call 07563 350335 Contact form
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
Wiper rules at the MOT
The tester checks that the wipers work, that they clear enough of the screen for the driver to see the road, and that the blades are in place and secure. Common fails include:
- Split, perished or missing wiper rubbers
- Blades that smear, judder or leave large unwiped areas
- A wiper that doesn't park properly or stops mid sweep
- Worn wiper arms that don't press the blade onto the glass
Winter is hard on blades. Frost, ice and grit from salted roads wear the edge quickly. Our guide to wiper blades in winter explains how to check them and when to change them.
Washer rules at the MOT
Washers must provide enough fluid to clear the windscreen together with the wipers. A blocked jet, a failed pump or a split pipe can all cause a fail, and so can an empty bottle. In winter, use a proper screenwash at a strength suited to the cold. Plain water freezes in the bottle and pipes, and washing up liquid can damage paint and rubber. See what to do when screenwash freezes.
Stickers, mounts and other obstructions
Parking permits, tax disc holders left on from years ago, sat nav mounts and dash cams can be a problem if they sit in the swept area. The same size limits apply. Mount them low in a corner, or behind the rear view mirror, outside zone A.
Quick checks before your MOT
- Sit in the driver's seat and look for chips and cracks in front of you, roughly a hand span either side of the steering wheel centre.
- Run the wipers on a wet screen. Look for smears and missed areas.
- Lift each blade and run a finger gently along the rubber for splits.
- Test the front and rear washers and check the jets hit the glass.
- Top up the screenwash.
- Remove or move anything stuck to the glass in the swept area.
These are among the easiest fails to avoid. Our lists of common MOT failures and MOT advisories explained cover other items worth checking.
How we can help
We don't carry out MOT tests, but our pre-MOT check at your home looks at the screen, wipers, washers, lights, brakes, tyres and more, so you know what's likely to pass. We can fit wiper blades, clear blocked washer jets and trace a dead washer pump on the driveway. Labour is £30 to £50 per hour and you get a quote before any work starts. Send your reg and postcode on WhatsApp 07563 350335 or use our contact page.
Want to pass your MOT first time?
Message us on WhatsApp with your reg and postcode, or use our contact form, for a price before any work starts.
WhatsApp for a free quote Call 07563 350335 Contact form
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
Frequently asked questions
What size windscreen chip fails an MOT?
Damage larger than 10 mm in the area directly in front of the driver (zone A) fails, and damage larger than 40 mm elsewhere in the area swept by the wipers fails.
Is an empty screenwash bottle an MOT fail?
The washers must supply enough fluid to clear the screen with the wipers, so a washer system that doesn't work, including an empty bottle, can fail. Top it up before the test.
Do split wiper blades fail the MOT?
Yes, if the blade is missing, insecure, or so damaged or worn that it doesn't clear the screen properly. New blades are a cheap way to avoid the fail.
Can stickers or a sat nav fail an MOT?
They can if they seriously obstruct the driver's view in the swept area, using the same size limits as windscreen damage. Move them to the edge of the screen or out of the wiper area before the test.
