I have the 2011 15" macbook pro radeon 1gb. While playing a game or doing heavy video editing the screen begins dimming and un-dimming repeatedly in 3 second intervals. The screen will dim for 3 seconds then get bright for 3 seconds and get dim again in a constant loop. Is this a symptom of overheating? How do I fix this?
MacBook Pro
Be careful to not let your hand move over the speaker grills. The backlit keyboard sensors are behind those speakers. When those lights change, they can affect the display brightness sometimes.
I use a mouse and my hands are not anywhere close to the speakers. I usually does this about 5 or 10 minutes after the fans kick into high gear.
Turn off the ambient light sensor and see if it still does it. System Preferences > Displays > Display tab > uncheck "automatically adjust brightness as ambient light changes".
Regards
OK I think I may have solved the problem but unfortunately have uncovered another. I will post what I found in case it may help others that have the same problem.
It seems that the reason the screen was dimming and un-dimming was because the computer was switching to battery mode and back to AC and because I had checked the "dim screen when running on battery" in the power management setting it dimmed and un-dimmed. I tested this out and played a 2 hour game of Starcraft II and no Dimming. While doing the test I did notice my battery level was going down even though I was plugged in. This brings me to my other problem. When I do gpu intensive tasks, the magplug on the side of my macbook turns from green to amber. The drain doesn't go down as fast as it would if I were just running on battery but it does go down. I played for about 3 hours last night and it went down to 72% despite having it plugged into a power source. Does anyone know is wrong?
Nothing is wrong — your MBP is operating as it's designed to do.
When your activity on the machine demands more than the 85W of power that the AC adapter can provide, the battery is drawn upon for the difference. Because the AC adapter is providing most of the necessary power, the battery doesn't drain nearly as fast as it would without the adapter connected, but it does drain.
You can reduce your chances of running into this by disconnecting all peripherals that draw their power from the computer, dimming the screen backlight as much as possible (reducing the ambient light level in your workspace will make this more tolerable), turning off keyboard backlighting, turning off Bluetooth and Airport if they're not in use, quitting all nonessential CPU- and GPU-intensive processes, and using the integrated GPU instead of the discrete one on a MBP that has both, if the integrated GPU is up to the task at hand. These steps will minimize the consumption of power for tasks other than the primary one.
You may well wonder why Apple didn't provide a higher-output AC adapter. Only Apple could answer that, and Apple hasn't. My guess is that pumping enough AC power into the machine to enable it to run flat out and charge its battery at the same time would generate too much heat for its cooling system to dissipate effectively.
Afterthought: in your MBP, the ambient light sensor is not behind the speaker grilles. It's 5mm to the left of the iSight camera lens in the top of the display bezel. This has nothing to do with your problem, but its location was misstated in one of the previous responses.
Thanks eww, that was useful information. I definitely don't feel better though. It seems like a design flaw to me and kind of makes me feel uneasy about running out of power. What happens if I wanted to play an all nighter? Having the battery limit the time I could use my computer even though i'm plugged in is disappointing. I'm new to the Apple world besides having ipods and iphones but have never experienced this on windows based laptops. Atleast the mystery is solved. Thanks
Display repeatedly dimming and un-dimming
