Windshield wiper arms are spring-loaded, to press the wiper blades against the windshield so they clean it properly. These springs are pretty strong, so when you’re changing wiper blades, you need to be careful.
I was changing the wiper blades on a customer’s car when the arm suddenly slipped out of my hand. Even though it was only a few inches away from the windshield, it was enough for it to crack the windshield. This was the first time it’s happened to me, but I’ve heard of it happening plenty of times. Often it’s when someone removed the wiper blade and then left the arm in the fully up position, and then it happened to slam back down on its own. When you change wiper blades, it’s safest to remove the blade and lower the arm back onto the windshield if you don’t have the new blade right there to install.
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