Why do the wipers on your 1991 park avenue slap on the downward stroke they hit the stops on the bottom of the windshield which makes a loud noise?

This answer is from my own past experiences. It is not guaranteed, but it has helped me and friends in the past. I have found that the wipers are sometimes incorrectly adjusted, somtimes due to years of use/adjustment slippage. The wiper motor drives the wipers with a drive arm. The actual wipers themselves are attached to this drive arm with a screw. If the wipers are hitting the park-stops on every wipe, the adjustment screw needs adjusted. Basically, turn the wipers off. Here is where it gets a bit tricky. The bottom part of the windshield, where the wipers recede, there may be a screw to open an access plate (probably plastic) where you can lower a nut driver (same as a screw driver, but with a socket end on it) and loosen the bolt below. God, this is hard to explain on a simple internet text message. Now, with the wipers off, and the screw loosened, manually move the wipers to their normally parked position, probably a very slight move. Now, lock that screw/bolt down. Tighten it and try the wipers once again. If the problem is still present, then the main bolt on the wiper motor itself needs loosened, repositioned, and tightened. I hope this helps.

First answer by Gsantander777. Last edit by Gsantander777. Contributor trust: 0 [recommend contributor]. Question popularity: 1 [recommend question]