Replace that switch! $21 at dealer... I think WorldPac is out of stock on these.
Remove the 2 screws at base of wood AC panel .. just above stereo. Then remove the ACC push button control unit by removing 6 screws (2 large, 4 small). Pull the unit out and then you'll have access to switch.
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi