Buick 2010 Lacrosse Owner's Manual page 217

Climate Controls 7-3
(Air Conditioning):
Rear Window Defogger
(Rear Window Defogger):
Do not try to clear frost
or other material from the inside
of the front windshield and rear
window with a razor blade or
anything else that is sharp. This
may damage the rear window
defogger grid and affect your
(Recirculation):
radio's ability to pick up stations
clearly. The repairs wouldn't be
covered by your warranty.