Screen doesn't work when not booted up with external monitor.

I've been having a peculiar issue with my MacBook (vanilla, not Pro or Air). When I turn it on after it has been shut down, I can hear the startup noise and the backlight turns on. I can not see anything on the screen, however.

If I connect an external monitor at this point, both screens start to work. If I move my cursor to the original (non-external) screen, that screen goes blank with the backlight still on.

Fortunately, the log-in dialog is on the external monitor so I am able to log in. Once I do, everything starts working normally. I am able to disconnect the external monitor and my MacBook will work fine from then onwards.

Is this a hardware/graphics issue? A software issue? How do I fix it so I can boot without an external monitor?

If it matters at all, I run Caffeine and F.lux, but I don't believe they are started up until I log in. Is it possible that one of them changed a setting somewhere?

It sounds like something in the NVRAM has suffered "brain damage" so let's try to reset it and see what happens. Go to the following LINK and follow Apple's instructions for resetting. If that doesn't work, you may have to reset the SMC also. See this LINK.

Also.... make sure you're not operating on battery.

chscag said:

It sounds like something in the NVRAM has suffered "brain damage" so let's try to reset it and see what happens. Go to the following LINK and follow Apple's instructions for resetting. If that doesn't work, you may have to reset the SMC also. See this LINK.

Also.... make sure you're not operating on battery.

Click to expand...

I tried resetting the NVRAM before posting this. Needless to say, it didn't work.

I haven't yet tried to reset the SMC as I am away from my tools right now.

I have discovered that if I set the color temperature in F.lux to 5200K or below, the screen starts working. If I move it above that, it goes dark. Does this provide any more info?

What do you mean about your last point? Make sure I'm not operating on battery when resetting SMC?

Thank you.