Welcome to AF.
Sounds like your switch control might hav a bad connection or the switch mech. is dirty.
I'd pull the switch panel out and check the plugs for corrosion. Wouldnt hurt to check the pass side switch too.
If they are ok, try shaking or blowing out the switch control. Some times debrie gets into them and they dont work properly.
Wiggling them side to side also can help clear the button under the switch.
Thier are pics and helpful info in this thread...
http://www.automotiveforums.com/vbul...d.php?t=891026
Hope that helps