You should check for defects, loose parts or worn-out blade elements on an intermittent basis. Wiper blades accumulate a thin film over time which may hinder their performance hence they must be regularly cleansed with mild soap solution. If the wiper blade elements are cracked, worn or warped or no longer clean adequately, these must be changed by brand new ones. Raise the arm assembly from the glass to create space and then push down the release lever so that you can detach the wiper blade assembly from the hook at the edge of that arm. To take off either of them pull away on the clip and remove its plastic cap until it locks into place. Turn around 90-degrees and disengage such from that arm. Attach a fresh wiper on this arm. A click is heard when connected properly.