Ford Mustang Owner's Manual page 80

Make sure you can see clearly through the
rearview mirror at all times. Do not block
your vision. If you cannot see through the
mirror, it could result in a collision,
injuring yourself and others.
Rearview Mirror and Lamp Assembly
(convertible only)
This rearview mirror contains two lamps which
function as courtesy lamps when the doors are
open. These lamps also function as map lamps
when the doors are closed and the rocker switch
is activated.
The rearview mirror with lamps
78
R WARNING