Not every worn blade behaves the same way.
Streaks That Stay in the Same Place
If the same narrow line appears after every pass, look closely at the corresponding section of the blade. A nick, small tear, or hardened section may no longer be removing water from that area.
This is especially annoying when the streak sits directly at eye level.
A Blade That Chatters Across the Glass
A chattering wiper does not glide smoothly. It grabs the windshield, releases, and grabs again as it travels.
You hear it before you even think about visibility.
Age-hardened rubber can cause this, but a dirty windshield, contamination on the wiping edge, or poor blade contact can contribute too. If cleaning the glass does not change the behavior and the blade is worn, replacement makes more sense than living with the noise.
A Hazy Film After Every Sweep
Smearing is different from leaving one narrow streak. Instead of clearing the water, the blade spreads moisture and road film over a larger area.
At night, that haze can become much more noticeable when headlights shine through it.
That is often the moment a driver realizes the blades have been getting worse for a while.
Do Not Wait Until the Blade Starts Coming Apart
A severely worn wiper usually gives plenty of warning before the rubber separates.
If you lift the arm and see torn material hanging from the blade, the service is overdue.
Once the wiping element begins pulling away, less of the blade contacts the windshield. Continue using it long enough and harder parts of the wiper assembly may get closer to the glass than they should.
The inexpensive part is supposed to take the wear.
Replacing the blade while the problem is still rubber deterioration is much simpler than allowing a damaged wiper to create another issue.