How to tighten a droopy rear view mirror?

Note: You may want to remove the mirror from the windshield first to make the following steps easier. It's not necessary, but it's up to you. If so, pry off the plastic cover at the top of the mirror stalk, disconnect the power cord, and then pull the mirror downwards and parallel to the windshield to remove it.

Method 1: On the back side of the mirror below the ball joint, there is a small round cover. Insert a sharp blade tip at the top of the cover and carefully pry it out. Underneath is the tip of the tension screw. It has a slot in the end of it that can be tightened with a small flat-blade screwdriver. Carefully replace the cover, inserting the bottom tab first, then snap in the top. If the mirror is still not tight enough, go to Method 2.

Method 2: Carefully pry off the rim bezel of the mirror, starting in the middle of the seam on the bottom, working your way around the edge. The bezel will pop off when you get past one of the ends. I used a pair of heavy guitar picks to keep the latches from snapping back into place as I progressed. Once the bezel falls off, the mirror assembly will dangle from the power cord. The Phillips tension screw is in the center bottom of the case; tighten it to suit, and make certain that the four bracket mounting screws around it are all tight, too. Then place the mirror assembly back in place and snap the bezel back into place, starting at the top.