Why wipers are not clean: In fact, wipers are always not clean, the main reason is that there is invisible dirt on the glass.

First, the car stopped at the bottom of the central air conditioner cool water tower, the cool water tower will tear the water after the particles fell on the glass to form a small white spot, after dry, it is difficult to completely clean;

Second, the car is parked under a tree, insect secretion of mucus stuck to the car glass;

Three, is the high speed run long distance to smash the insect carcass mucus. Because these things stick to the glass and are difficult to remove completely with water and cloth (just not visible), they create uneven surfaces on the glass. In this way, when using wipers, the glass appears scraping the situation.