Blade inspection
Contamination of either the windscreen or the wiper blades with foreign substances can reduce the effectiveness of the windscreen wipers. Common sources of contamination are insects, tree sap, and hot wax treatments used by some commercial car washes. If the blades are not wiping properly, clean both the windscreen and the blades with a good cleaner or mild detergent, and rinse thoroughly with clean water.
CAUTION
To prevent damage to the wiper blades, do not use petrol, kerosene, paint thinner, or other solvents on or near them.
TIP
Commercial hot waxes applied by automatic car washes have been known to make the windscreen difficult to clean.