Old, worn out or defective windshield or windscreen wipers cause impaired vision and, according to the consumer information site Automedia, are the cause of as many as 20 per cent of all accidents. Wiper blades should be inspected every six months and replaced as soon as they begin to lose effectiveness at clearing moisture from the windshield. Several different wiper problems can cause visibility issues.
Wiper blades may make noise during operation. This can be a scraping, thumping or screeching sound. The wiper blades should be checked for rubber which has decayed or torn and is loose, slapping against the glass. The rubber blades may also be stiff and not flexing to fit to the windshield, causing them to scrape unevenly along the surface of the glass and "chatter." If a wiper blade is completely missing, or if one section is gone, the metal of the wiper arm will scratch against the glass, causing a shrill screeching. This needs to be resolved immediately, as the windshield itself can be damaged from being scraped repeatedly by a bare metal wiper arm.
If a windshield wiper consistently makes streaks on the glass, it may be dirty or it may need to be replaced. The first step is to try cleaning the blade and glass underneath it with a soft rag. Put some windshield washer fluid on the rag or use a bit of dish-washing liquid. Wipe thoroughly and try the wipers again. If the streaking persists, it is time to change the wiper. Often worn wiper blades will feel stiff, or they may show signs of wear such as cracks and chips. Any of these signs is a good indicator that it is time to change the rubber wiper blades.
When the windshield wipers won't move after being turned on, the culprit is likely to be the wiper motor. To verify this, it is important to first make sure that the wiper blades are not stuck to the windshield by sap or ice. If the blades still won't move, the problem is likely to be a bad wiper motor or stripped gears. Gears can be stripped by attempting to run the wipers while the blades are being held immobile by ice, snow or debris. Some wipers prevent damage with a release mechanism which prevents damage, but in many cases gears will be damaged or the motor burnt out. In this case it will be necessary to replace the damaged components, most likely the entire motor assembly.