blower

my wife's 2006 impala has an issue with the blower. often when you turn on the heat, air, etc, the blower doesn't work. you can hit the top of the dash JUST RIGHT and it will start up. anyone else experienced this or know what exactly the culprit might be?

My 2002 chevy trailblazer's blower for the heat and air will only work up to setting 4. when i turn it to setting 5 it turns off. How do I fix this?