My Toyota headlights are cloudy so it failed its MoT. Will an abrasive cleaner damage them?

Q. The headlamps of my ageing Toyota Yaris have clouded over, resulting in an MoT failure. A garage applied an abrasive liquid normally used for bodywork to clear the glass for a retest. I’ve since been told this may have removed a coating that protects the lamps from sunlight damage. Is that true?
LF, Manchester

A. You are right that your headlights need a coating to protect them from ultraviolet (UV) light. After defogging the lights, your garage should have reapplied it. If it didn’t, it’s easy enough to do it yourself.

Fogging occurs because UV light from the sun slowly degrades the lamps’ plastic surface. The plastic develops tiny cracks, which cause the clouding by scattering light in different directions.

To protect them you need a product such as Meguiars Headlight Protectant (£8.99 from meguiars.co.uk), a clear solution that sets on the surface of the headlamp to form a barrier against UV rays. If you reapply it three or four times a year the lamps should remain adequately protected.

You can clear a fogged lamp yourself, and I have had good results with the three-step Turtle Wax Headlight Lens Restorer kit (£12.99 from gear4yourcar.co.uk). Once you’ve cleaned the lamps and masked surrounding paintwork to avoid damaging it, polish the headlamp surface with the lens-clarifying compound, using a soft cotton cloth.

If the fogging persists, polish the headlamps with the abrasive cleaning pads and spray-on lubricant that come with the kit. This will progressively cut through the outer layer of plastic that has the tiny cracks. The final stage of restoration is to rub the lamps with the kit’s UV-protection wipes to shield them from further degradation.

INSPECTOR GADGET
Dave Pollard has written several Haynes manuals and has tested just about every car-related accessory – read more from Dave here.

GOT A PROBLEM?
Email your question to carclinic@sunday-times.co.uk or write to Car Clinic, Driving, The Sunday Times, 3 Thomas More Square, London E98 1ST, with a daytime phone number, your address and as much detail about your car as possible. We can’t reply in person, so don’t send original documents or SAEs. Advice is given without legal responsibility.

Search for and buy used cars here