My left side (Passenger side) mirror doesn't "lock" into its open position. It's hard to describe but you know how there are 2 positions which it "snaps" into closed or open...... well it doesn't really do that and it freely swivels between those two positions.

I'm assuming that there is a bolt that it swivels on and that it just needs tightening. Am I correct and if so is there a way I can fix it without pulling the whole door trim off and pulling off the mirror?