Windscreen woes cause for reflection

By Paul Mooney on Sat, 9 Dec 2017

Over the past 12 months, I've had a rather bad run with the windscreens of various test cars supplied to Drivesouth for appraisal.

Half a dozen have taken stone hits sufficient to leave a mark, including two serious enough to warrant a windscreen replacement or repair. I've also driven another test vehicle that came into my care with significant windscreen damage, and was returned with that screen requiring replacement.

Interestingly, all three incidents of serious damage have been to the windscreens of SUVs.

The first took its big stone hit courtesy of a stock truck, while motoring along SH1 between Waikouaiti and Palmerston. The stone was big enough for me to see it coming. The impact gave everyone in the vehicle a huge fright and a long crack immediately spread from the impact crater. I stopped in Palmerston to phone the vehicle's owners and ask them to arrange for a replacement windscreen to be sent south.

The second hit came on a heavily gritted portion of SH85 between Wedderburn and Omakau. It was just a small, sharp crack of an impact, but enough to leave a mark on the windscreen that showed all the signs of becoming the starting point for a crack. The final destination that day was Wanaka, and while that town's windscreen repairers couldn't fit me in for a repair, they provided a patch to put over the chip mark to prevent moisture entering (which makes it harder to repair).

As far as I know, the windscreen got the heat treatment when I returned the car to Dunedin, avoiding the need for a full windscreen replacement.

Last and not least, the vehicle I collected with a significant crack a few weeks ago. Well, the replacement windscreen was already on its way, which was just as well, since the 5cm crack had expanded to 20cm by the time I returned the vehicle to the local dealer.

Chatting to staff from that dealership reminded me windscreen replacement isn't the straightforward job it once was. That's largelybecause a modern windscreen not only allows visibility but does much to protect a vehicle's occupants from the elements. 

As well as being laminated for strength, it may be designed to repel harmful UV radiation, and, if it is special acoustic glass, to minimise noise intrusion. It may also be the screen for a head-up display, and the item through which rain and light sensors operate to enable automated rain-sensing wipers and auto-dipping headlights. It may incorporate a windscreen heating system, and sometimes (though more often in the back window) antennas for cellular, GPS and radio systems. Most importantly, a windscreen provides a substantial proportion of a vehicle roof's rigidity and is the surface against which the front passenger's airbag deploys.

It's a crucial part of a modern car then, but one we take for granted until a stone flies up suddenly and leaves its calling card.

David Thomson