GMC 2000 Sierra - Manual (Page 133)

yellow blue
2-55
Electrochromic Inside Rearview Mirror
with Compass (If Equipped)
When on, an electrochromic mirror automatically dims
to the proper level to minimize glare from lights behind
you after dark.
The mirror also includes an eight - point compass display
in the upper right corner of the mirror face. When on,
the compass automatically calibrates as the vehicle
is driven.
Mirror Operation
The right side of the switch located at the bottom of the
mirror turns the electrochromic mirror on and off. The
LED, located to the right of the switch, will come on
when the electrochromic mirror is turned on. To turn the
mirror on, press and hold the MIRROR button for three
seconds. The mirror will darken and remain dark until
the button is released. To turn the mirror off, press and
release the MIRROR button.