Strange NAV headunit question

[Corellian Corvette]

Got my hands on another 4.6is parts car and was able to get some good parts from it. One thing I grabbed was another NAV headunit since mine has some of the circular spots. I plugged it in, and the screen is nice but it’s very dim!

I went into settings to adjust the brightness — but there is no brightness setting?? This is the only head unit I’ve seen missing a brightness option.

Any ideas? This screen is much nicer than the one in my car so I’d like to make it work if possible!