The windshield and wiper blades should also be clean to ensure the maximum fare or the longest life of the elements as dirt, sap of trees and tar on the road may lead to streaking, smearing and degradation of the blade. Washing the windshield by using a commercial glass cleaner should be done at least once a month and wiping off the rubber blades with a wet rag should follow. Do not use your hands to move the wipers over the windshield so as not to damage the motor and the drive mechanism. To install or verify the wiper blade element, push the wiper switch to the LOW speed position, and the ignition switch to the ACC position and get the blades into a position about right before pressing the ignition switch to OFF. Investigate the wiper blade parts whether they have cracks, breaks, or tears, and instantly replace them in case any damage has occurred. Replacement time will depend on the usage, however, ozone degradation will normally shorten the life of the elements to a period of one year. Where the wiper pattern is smeared or streaked, or chattering across the glass the elements are to be changed, preferably in pairs. When refills, with aftermarket blades, are used, note that different varieties of refills can be used, and it is important to carefully follow the instructions of the part manufacturer. Always make sure that all frame jaws are locked when refill is being inserted and locked because when metal blade holder comes in contact with frame and glass during operation then it creates scratches.