MOT & Your Car Windows: The Full Lowdown

When your vehicle approaches its annual MOT test, a myriad of components are scrutinised to ensure it meets the minimum roadworthiness and environmental standards. While the focus often falls on brakes, tyres, and lights, the condition and functionality of your car's windows and glass are equally critical and frequently a source of unexpected MOT failures. It's not just about being able to see out; it's about safety, visibility, and adherence to specific regulations. Understanding these requirements can save you time, money, and the hassle of a retest.

The MOT test is designed to ensure that vehicles are safe to be on the road. For windows, this primarily translates to ensuring the driver has a clear and unobstructed view of the road ahead and to the sides, and that the glass itself is structurally sound and free from defects that could compromise safety or visibility. This extends beyond just the windscreen to include side windows, rear windows, and even the functionality of electric or manual winding mechanisms.

The Windscreen: Your Primary View

The windscreen is, without doubt, the most critical piece of glass on your vehicle when it comes to the MOT. Any damage here can significantly impair the driver's view and, in some cases, compromise the structural integrity of the vehicle. The MOT test divides the windscreen into specific zones, and the permissible damage varies depending on which zone the damage falls into.

Windscreen Zones Explained

• Zone A: This is the most critical area. It's a 290mm wide strip centred on the steering wheel, extending from the bottom of the windscreen to the top, or within the swept area of the wiper blades. For vehicles with a maximum gross weight of more than 3,500 kg, the zone is 350mm wide. This area is directly in the driver's line of sight.
• Zone B: This is the remainder of the swept area of the windscreen, outside of Zone A.
• Unswept Area: Any part of the windscreen not cleared by the wiper blades.

Permissible Windscreen Damage for MOT

The rules for chips and cracks are quite strict, especially in Zone A. Even seemingly minor damage can lead to an MOT failure.

• In Zone A: No damage (chip or crack) larger than 10mm is allowed. This is roughly the size of a 5p coin.
• In Zone B: No damage larger than 40mm is allowed. This is roughly the size of a £2 coin.
• In the Unswept Area: Damage here is less critical for the MOT, but extensive damage could still be an advisory or a failure if it affects the structural integrity or security of the glass.
• Cracks: A crack that extends across more than one zone or significantly impairs the driver's vision will likely result in a failure, regardless of its individual length if it's within the critical zones. A single crack over 40mm anywhere in the swept area will fail.

It's important to note that any damage that is likely to shatter the glass, or is positioned where it could cause injury, will also lead to a failure. Furthermore, any repairs made to the windscreen must be of a professional standard and not impair the driver's vision.

Side and Rear Windows: Clarity and Tinting

While less critical than the windscreen for direct forward vision, side and rear windows are still subject to MOT checks, primarily concerning their condition and tinting levels.

Condition of Side and Rear Windows

Side and rear windows should not be excessively damaged or cracked to the point where they obscure vision or pose a safety risk (e.g., shattered glass). Minor chips or scratches are generally acceptable as long as they don't significantly impede the driver's view through the required fields of vision or compromise the integrity of the glass.

Window Tinting Regulations

This is a common area of confusion and a frequent cause of MOT failure. The rules for tinting vary significantly between the front and rear windows.

• Front Windscreen: The light must be able to pass through by at least 75% (measured as Visible Light Transmission, or VLT). The top 6 inches (152mm) of the windscreen can have a darker tint, provided the VLT is at least 70%.
• Front Side Windows: (Those next to the driver and front passenger) The light must be able to pass through by at least 70% VLT.
• Rear Side Windows and Rear Windscreen: There are no specific legal limits for the darkness of tints on these windows. You can have them as dark as you wish, provided the vehicle has two working wing mirrors.

If your front windscreen or front side windows are tinted beyond these limits, your vehicle will fail its MOT. It's crucial to be aware of these limits, especially if you've bought a car with pre-existing tints or are considering aftermarket tinting.

Window Functionality and Other Glass Elements

Beyond the condition of the glass itself, the functionality of the windows and other related components are also assessed.

• Power and Manual Windows: The driver's side window must be able to open and close. While there isn't a specific requirement for all other windows to be fully functional, a window stuck in a position that obstructs the driver's view or poses a safety risk (e.g., stuck open in a way that allows objects to enter the vehicle easily) could lead to a failure or advisory. The primary concern is the driver's ability to see and operate the vehicle safely.
• Windscreen Wipers and Washers: These are absolutely essential for maintaining clear visibility in adverse weather. The wipers must clear the windscreen effectively, covering the required swept area. The washer system must deliver fluid to the windscreen. Both must be in good working order.
• Rear-view Mirrors: While not windows, mirrors are glass components vital for visibility. All required mirrors (driver's side, passenger's side, and interior) must be present, secure, and provide an adequate view to the rear. Cracked or missing mirrors will result in an MOT failure.

Summary of MOT Window Check Criteria

To provide a clearer picture, here's a summary of common issues that lead to MOT failures related to windows and glass:

Pre-MOT Checks for Windows and Glass

Performing a few simple checks before your MOT can help you identify potential issues and address them in advance, saving you a retest fee and hassle.

1. Inspect Your Windscreen: Carefully look for chips and cracks. Pay close attention to Zone A (the area directly in front of the driver). Measure any damage to ensure it's within the permissible limits. Consider professional repair for chips, as this is often much cheaper than a full windscreen replacement.
2. Check Your Wipers: Turn them on. Do they clear the screen effectively without streaking or juddering? Lift the wiper arms and check the rubber blades for tears, hardening, or perishing. Replace them if necessary.
3. Test Your Washers: Ensure the washer jets are clear and spray effectively onto the windscreen. Top up your screenwash reservoir.
4. Examine Window Tints: If you have tinted windows, especially on the front, and are unsure about their legality, it might be worth getting them professionally checked or removed if they are too dark. Remember, rear window tints are generally not an issue.
5. Check Window Functionality: Operate your driver's side window. Does it go up and down smoothly? If not, investigate the cause. While other windows are less critical, ensuring they operate correctly is good practice for safety and convenience.
6. Inspect Mirrors: Ensure all mirrors are present, secure, and the glass is intact. Adjust them to ensure they provide a clear view.
7. Clear Your View: Remove any stickers, sat-nav mounts, or air fresheners that might obstruct your view, especially in Zone A of the windscreen.

Frequently Asked Questions About MOT and Windows

Q: Can a small chip on my windscreen fail my MOT?

A: Yes, if the chip is in Zone A (the critical area directly in front of the driver) and is larger than 10mm in diameter, it will result in an MOT failure. In Zone B, chips larger than 40mm will fail. Even small chips can spread, so it's always best to get them repaired promptly.

Q: Are tinted windows an MOT fail?

A: It depends on which windows are tinted and how dark they are. If your front windscreen allows less than 75% of light through, or your front side windows allow less than 70% of light through, they will fail the MOT. Rear side windows and the rear windscreen can be tinted to any level of darkness.

Q: Do electric windows need to work for the MOT?

A: The driver's side window must be able to open and close if its position impacts the driver's view or the safe operation of the vehicle. While there isn't a specific requirement for all other windows to be fully functional, a window stuck in a position that obstructs the driver's view or poses a safety risk could lead to a failure or advisory.

Q: What if my rear window is smashed but I can still see with my mirrors?

A: A smashed rear window will likely result in an MOT failure. While you might be able to see via your mirrors, the shattered glass poses a significant safety hazard, and the integrity of the vehicle's structure could be compromised. It also fails the basic requirement of being in a 'good and safe' condition.

Q: My windscreen washer jets are blocked. Will this fail the MOT?

A: Yes, if the windscreen washer system does not effectively clean the windscreen (e.g., blocked jets, insufficient fluid, or a faulty pump), it will result in an MOT failure. Clear visibility is paramount.

Q: Can I have stickers on my windscreen for the MOT?

A: Small, unobtrusive stickers (like a tax disc holder or parking permit) are generally fine if they are outside the critical swept area of the wipers and do not obscure the driver's view. However, any sticker or obstruction within Zone A or that significantly impedes the driver's visibility will result in an MOT failure.

Q: What if my side window is stuck open?

A: If a side window is stuck open in a way that allows foreign objects to easily enter the vehicle, or if it significantly affects the structural integrity or safety, it could be an MOT advisory or even a failure. The primary concern is safety and the prevention of injury.

Conclusion

Your car's windows and glass are far more than just transparent barriers; they are integral components of vehicle safety and functionality. The MOT test rigorously checks these elements to ensure they meet the necessary standards for clear visibility and structural integrity. By understanding the specific requirements for windscreen damage, window tinting, and the functionality of wipers and washers, you can proactively address any issues before your MOT. A small chip repair or a quick check of your washer fluid can make all the difference between a pass and a fail, ensuring your vehicle remains safe and roadworthy for another year.

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