I had the same issue. I cleaned the contacts as suggested and it works great now. Saved a bunch of money and it was easy to do. Thank you for sharing.

 

I've got a 2005 SC430, and did not find much under that category. The issue......mirrors worked intermittently, then both just went completely out. Don't work in reverse either. My switch comes out slightly different from the LS, but essentially sliding the plastic tool under the bottom of the panel holding the switch, and worked my way around and slid right out. Not much room to manipulate the wires, but found if I removed the mirror connector first and security connector second, worked pretty smooth.
So got the thing apart....zero corrosion. Kind of rubbed the grease around and reinstalled. Nothing. Read a bit more and found others that had zero corrosion, and cleaned the connectors. So pulled it apart again, used isopropyl and as far as I can tell, the grease was the issue. The connectors had sort of a matte finish before cleaning, and after cleaning they were mirrors. Put the thing back together, and blammo..........works. I'll pick up the dielectric grease later today, give it a light coating, and button it back up. For those who are not using the grease, yes the switch is not used much but to prevent further corrosion and wear, I'd highly recommend using the grease.

 

I had the problem and replaced the entire switch with one I ordered and it now works the mirrors ok. My original quit working after the bodyshop had to pull the mirrors off - not that they broke anything but after I got the car back from the bodyshop the switch would not work the left mirror for anything. I replaced the entire switch combo and everything started working again. I was able to remove just the mirror adjustment part by gently lifting the plastic tabs holding it into the frame and it slides out - and swapped it out with my original cluster to keep the color correct. .

 

Way to go - I just replaced ( yeah - im a parts cannon sometimes) good going