alchang32

Okay today when i was starting to drive and leaving my house. i rolled the passenger side window down. When i pushed the one-touch for the window to roll down....after the window went completelly down after 2 seconds when it went down i hear a knock. When i put it back up no sound. when i put the window down half way no sound. only when the window is completelly down it make the ONE KNOCK sound. Which only occured on my passenger side...

a little help my friends?

Thanks!