CHEVROLET 1999 Corvette - Manual (Page 97)

yellow blue
2-45
Headlamp Doors
The headlamp doors are designed to open when you turn
the headlamps on, and close when you turn the
headlamps and parking lamps off. If you turn the
headlamps on, then turn the headlamp switch back to
the parking lamps setting, the headlamp doors will
stay open.
You can open the doors manually using the knob next to
the headlamp assembly. Turn the knob counterclockwise
until the doors are open.
The headlamp doors should be open when driving in icy
or snowy conditions to prevent the doors from freezing
closed and when washing the vehicle to help clean
the headlamps.
NOTICE:
In order to avoid possible contact of the hood to
the headlamp doors, care should be taken in
raising the hood with the headlamps up, or shut
off the headlamps prior to opening the hood.