Windscreen Maintenance Guide: Looking After Your Car Glass

Hiding in plain sight, automotive glazing has a tough life. Not only does it serve structural and safety tasks but it also must isolate noise and withstand considerable pressures from air flow and even impacts.

While it serves these tasks admirably, neglect can cause damage and breakages are not uncommon. To assist you, our technical help division has assembled the most popular glass-related questions from our members:

Practical tips for windscreen maintenance

It may sound obvious but keeping glass clean is our top maintenance tip, especially as regular cleaning has safety benefits.

While most drivers recognise the necessity of clearing away baked-on deposits and smears, regular cleaning can also remove the greasy film that builds up inside. This can exacerbate oncoming headlamp dazzle and is worth considering regularly if you drive frequently at night.

Worn windscreen wipers can create tiny scratches in the glass, which can also exacerbate nighttime dazzle. Most wiper manufacturers recommend annual replacement as vital glass maintenance, rather than when the MOT Tester insists.

Ensure that your washers work, because driving a car with an empty (or even frozen) screen-wash bottle is an offence.

Click here for our other tips on car maintenance.

Can I use anti-freeze, or washing-up liquid, in my screen wash bottle?

Using either of these products risks creating films on the screen and damaging the paintwork. We recommend that you use a dedicated windscreen washer additive not only for its anti-freezing properties in winter but also to help reduce the risk of Legionnaires’ Disease developing within the bottle during summertime.

What does the MoT Test say about wipers and washers?

The annual inspection in England, Scotland and Wales requires an adequate quantity of fluid to clear the windscreen. It would not matter if the screen wash bottle is empty, frozen, or leaking. If insufficient fluid is delivered, the car will fail the inspection.

Rear wash/wipe performance is not assessed. Yet, keeping it working is prudent. On cars used after September 2009 and equipped with LED, or HID, headlamps, inoperative lamp washers will fail the test. Washers that do not work on halogen headlamps washers will still pass.

The windscreen wipers are checked too. Obvious degradation, such as split rubber blades and broken springs, will fail. Tester discretion determines what comprises wiper efficiency at clearing the glass. The wiper mechanism should also park automatically, when switched off.

Can a sticker cause an MoT windscreen failure?

Should the examiner conclude that advertising stickers, or air fresheners, obstruct your vision, the car might not pass. Should the tester feel that removing them would risk damage, the test might be refused, or even aborted.

Can I have any stickers fitted to my front or rear screens?

Common sense must prevail. Several small stickers may be harmless, but obscuring your view with large “baby on board” placards and cuddly toys can constitute an offence under The Road Vehicles Construction and Use Regulations.

These carry a potential maximum fine of £1,000 or, if combined with irresponsible actions on the road, could land you with a prosecution for careless driving.

Are there any regulations about mounting Sat Nav / mobile devices on front windscreens?

The official stance is that all glass should be maintained so the driver's vision is not obscured.

While this is not definitive, you could mount these devices away from the areas swept by the wipers and argue your case, should you be stopped. Remember that the Highway Code states that:

‘Windscreens and windows must be kept clean and clear of all obstructions.’

Therefore, you could attach your phone cradle to your dashboard/air vents to be sure.

Can a windscreen crack cause the car to fail its MoT?

Recent changes to the MOT Test have resulted in less stringent windscreen examinations. Today, even cracked glazing can pass. This is because the assessment area focusses on two areas. The first is “Zone A”. This is a 290mm area in front of the windscreen, based on the steering wheel’s centre line position.

Any damage, or obstruction, including an adhesive sticker, within this area must fit within a 10mm diameter circle. The second area is swept by the wiper blades. Damage here can be larger but no more than 40mm in diameter.

Are window ‘Tints’ against the law?

Tinting windows has become a popular modification. While measurements are not performed during the MoT Test, British law is specific on what is permitted. Enforcement comprises random roadside checks by the DVSA, so do not presume that an MOT Test pass on your tints mean they are sanctioned as legal.

For cars used after 1 April 1985, the car windscreen and front side windows must let through 70% of external light into the interior and 75% for the windscreen.

Should you drive, or sell, a vehicle with excessively tinted front and rear windows, you will fall foul of Regulation 32 of the Road Vehicle Construction and Use 1986. However, prosecution is unlikely, provided that you cooperate with the police to have the vehicle rectified.

The bottom corners of the windscreen in my car are turning white. Should I be concerned?

While unsightly, the “milky” layer results from water seeping between the plastic and glass layers of the laminated screen, causing them to separate. While not an ideal situation, this would not fail a MoT but it is likely your windscreen is slightly weakened.

What should I do, if my windscreen develops a stone chip?

Even small chips risk developing into cracks from impact, or even temperature variations. Having the chip assessed and filled by a professional company not only restores strength but also, should you act quickly, reduces the chance of dirt entering the crack and compromising the repair.

If the chips, or resultant cracks, are larger than 10mm/40mm in diameter, depending on their location, it may not be worth having a windscreen repaired. Instead, budget on replacement.

Most car windscreen insurance policies have terms covering windscreen repair and replacement, so check the wording carefully.

Is windscreen replacement a DIY task?

It depends. Many classic cars have windscreens held in the frame by a rubber seal. In many cases, the only windscreen replacement cost is the screen itself, flexible sealant and, maybe, the rubber seal. All that is needed is a piece of string and a keen assistant to install them.

Modern cars are very different. Their windscreens form part of the body structure and are bonded into place with a structural adhesive.

Therefore, specialist knowledge and equipment are essential. A windscreen that is not attached to the car bodywork properly will weaken the structure and could blow out, should an airbag inflate.

What should I do if a windscreen, or side window, breaks?

As they comprise two panes of glass between a layer of plastic, modern windscreens tend to crack, rather than shatter. In many cases, it would be safe to drive the car either home, or to a place to be repaired. Should you be uncertain, contact your roadside assistance/breakdown provider.

However, side windows may be toughened rather than laminated. When they break, they do not produce sharp glass sections but small, blunt glass balls. However, tiny sharp shards of glass can also be produced.

Should a toughened window shatter, the best approach is to stop when safe and call your breakdown provider for assistance.

Continuing on your journey with a broken toughened window risks further glass particles entering the interior, or being ejected onto the road, where they could harm other road users.

DISCLAIMER 

The information on this Site is provided on the understanding that GEM Motoring Assist is not rendering legal or other advice. You should consult your own professional advisers as to legal or other advice relevant to any action you wish to take in connection with this website. 

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