Hi khan6530,

Please share the operating system installed. Press the key combination of 'Fn' key + the 'Right Arrow' key and it should cycle through auto, off, and on.

If the key combination does not work. You may try the following steps which might help:

• Click on the link http://dell.to/QjjZDA
• Enter the Service Tag of your system and select the operating system.
• You will find the 'Dell Ambient Light Sensor' application under 'Application'.
• Click on 'Download File'.
• Select 'For Single File Download via Browser'.
• Click on 'Download Now'.
• Save the driver on your desktop.
• Once the driver is saved on desktop, right click on it and select 'Run as administrator'.
• Install the application by following the on screen instructions.
• Restart the system and check functionality.

Hope this helps. Please reply if you have any questions.