Sony nav-u Guide De Démarrage Rapide page 9

Note
Clean the surface of the suction cup with a soft, damp, lint-free cloth if it becomes dirty
US
and attachment strength weakens.
To install on the dashboard
Clean the attachment surface of the dashboard, apply the on dash plate, then
attach the cradle.
The following steps are the same as for installing on the windshield.
Note
Choose the attachment location carefully before applying the on dash plate.
The on dash plate cannot be reapplied once removed.