Brightness resets on bootup

[Andy & Apple]

I've had the brightness down to about 1/3 from max setting (default), and it's been like this for over a year. Lately, everytime I boot up the brightness setting is reset and the screen is at max brightness, even though I had never set it that high the last time I was using it.

What am I using? 20" iMac OSX (2009)

 

[chscag]

Try resetting the System Management Controller (SMC) as that controls the ambient light sensor. See the following Apple KB article.

Regards.