CITROËN DS4 Owner's Handbook Manual page 98

Rear view mirror
Adjustable mirror providing a central rearward view.
Equipped with an anti-dazzle system, which darkens the mirror glass: this reduces the nuisance to
the driver caused by the headlamps from following vehicles, low sun...
As a safety measure, the mirrors should be adjusted to reduce the "blind spot".
Manual day/night model
Adjustment
Adjust the mirror so that the glass is
directed correctly in the "day" position.
Day/night position
Pull the lever to change to the "night"
anti-dazzle position.
Push the lever to change to the normal
"day" position.
Automatic day/night model
By means of a sensor, which measures the
light from the rear of the vehicle, this system
automatically and progressively changes
between the day and night uses.
In order to ensure optimum visibility
during your manoeuvres, the mirror
lightens automatically when reverse
gear is engaged.