MacBook Pro screen goes full brightness

I'm not sure these forums are monitored by Apple employees as I rarely if ever see a response. What I'd really like to see (HEY APPLE PERSON!) as standard process, is a simple acknowledgment of a reported bug. I don't expect a miraculous root cause explanation or firm timeline for resolution. It would be good if an Apple support person would simply post "Hello! We are sorry you are having a problem with an Apple product. Apple engineering teams are aware of this issue which has been logged as incident report #xyz123 and are working to resolve it as quickly as possible. You can check status by number at this website: www.apple.com/bugs".

Or something like that. That would feel so much better than reporting bugs into the void, hearing nothing back, and then waiting while months or years pass without resolution.

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Add Text button to include the report in your reply. How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck so that it can get additional information from the Console and log files for the report:

ALSO:

Then we can examine the report and see if we can determine the root of the problem.

Hello alekseyfromsan francisco and welcome to Apple Support Communities.

I see you're having an issue with screen brightness when attaching an external monitor.

Are you connecting the monitor after the Mac is already running or is it connected prior to startup?

What happens if you boot into safe mode?

Use safe mode to isolate issues with your Mac - Apple Support

Cheers.

I see none of the usual suspects in the report. Boot into Safe Mode (Use Safe Mode to isoloate issues with your Mac), set the brightness and reboot normally. Check the brightness setting again.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing. 

Well.. it is still working here. What could I have made different from you? Before following the procedure below I disconnected all external devices (also the charging since I am charging either from the e-GPU or from the a Thunderbolt dock). I am running Mac OS Catalina from a clean install, not an update of an older installation. I have had the issue on my external monitor (LG 5K) since I installed Catalina.

To be honest I can't remember if I connected my Mac before doing the last step of the safe start or not. But I think I did not connect it. When booted up in safe mode at the final step I did check the monitor setting. At that time it was at 100% and had reverted back to auto-setting. I switched to manual setting and reduced the intensity. I switched off my Mac and re-booted with all devices connected. Now I changed the monitor intensity for the external screen. I shut-down and started again and it was still at the lower setting.

alekseyfromsan francisco

User level:

Level 1

(27 points)

macOS

Speciality level out of ten: 1

Jan 14, 2020 1:57 AM in response to mountainman3520

What might help here is the following.

1) Reset SMS. Shut down Mac, then press all togerther Shift+Control+Option then Power button and keep it for at least 10 seconds.

2) Reset NVRAM. Shut down Mac, then press Option+Command, then 'P' and 'R' keys. Keep them pressed for at least 10 seconds.

3) Do a safe boot. Shut down Mac, then press Power and keep Shift button until the Mac starts to boot. Login into safe mode, then restart.

I am not sure what step specifically helps, but it looks like it's working better now.

I posted this reply in regards to the iMac, but it also addresses laptops. The problem appears to be in the SMC. This link (https://support.apple.com/en-us/HT201295) tells how to reset the memory in desktop and laptop computers.

The computer does boot with the display appearing to go to full bright. However, as it continues to boot the brightness returns to where I had set it prior to shut down.

Hope this helps

Hi Stephen,

as longstanding Apple veterans we clearly still have faith in the product but I must admit that my patience has been wearing thin since replacing my old MacBook Pro with this new (replacement) 16 inch 2019 model.

Unfortunately the visit to the Apple reseller this afternoon was a complete waste of time, as I guessed it would be - I had been sent there by Apple support who booked the appointment, ostensibly in order to replicate the problem using other monitors attached to the MacBook Pro. Not only did the store not have any monitors (or cables) available but they said that this often happens with customers being referred by Apple to investigate issues they are not in a position to undertake, other than basic diagnostics!!

Anyway to keep the response brief-I got back onto Apple, relayed my experience and annoyance to a senior support manager, who to give him his due, is taking personal responsibility for the issue and has escalated the issue up to the engineering section for their information. It's likely to be next week now before we get a response possibly but I will certainly keep people posted here regarding the outcome when I hear anything. They didn't seem to be aware (on their own databases) of the discussions about the issue happening on this forum either until I pointed it out.

The previous MacBook Pro was returned as I discovered that the ambient light sensor wasn't functioning at all and further complicating the current issue with the ambient lighting levels when connected to an external LG 5K superfine monitor.

Other issues have included dictation (which I use constantly) not functioning when MacBook Pro in clamshell mode plus other bugs in how it now behaves - see my other post here:

https://discussions.apple.com/thread/250734261

Engineering investigating this as well.

Issue with voice control (as opposed to dictation) which only works effectively if language English (United States) is selected when based in UK - this seems to be concerned with how Siri integrates with voice control and the servers used for transmitting the information. If you select English (UK) the latency is so bad it's unusable.

A possible overheating issue (very hot to touch in panel above Touch Bar) on the previous machine when connected to the 5K monitor.

Migration assistant didn't work (froze on each occasion) when setting up machine and had to resort to selective manual file transfer.

Individually some of these issues might not seem particularly critical, nor do they prevent use of the machine but collectively they add up to a great deal of frustration on my part, with hours spent with Apple support trying to diagnose (at my expense) issues that should have been resolved or tested prior to release.

Many thanks for the LG link and I'm hoping the majority of these issues can be resolved (eventually) - like everyone else I simply want to use the machine for the purpose for which they were made - being creative and productive, not spending 20+ hours on the phone to Apple Support (who are usually helpful) plus countless other hours dealing with the issues beyond that.

I'll keep you all updated once I receive any news.

Best regards.

I have the same issue. I have my iMac 2019's ( Catalina 10.15.2 ) display brightness set to 50% and manual control. Every time I unlock it, it brightens to 100% , and I have to manually adjust it back to 50% using the magic keyboard brightness controls. I don't change anything else.

• Lock it or let the display go to sleep on it's own.
• Unlock it ( usually with Apple Watch )
• Brightness for Retina changes to 100%

Hi, I got exactly the same issue, as I'm working in photography I need to have my screens stable and calibrated perfectly. The prob appears randomly, some times it takes acouple of days. I calibrate my screens, the 2nd screens is a graphic tablet Huion Kamvas pro 16" premium and my MBP is a 15" 2019, 2,4 GHz 8-Core Intel Core i9, 32 GB 2400 MHz DDR4, Radeon Pro Vega 20 4 GB running Catalina 10.15.1 (19B88), everything seasms OK and then a couple of days later when i start graphic tablet and my MBP the brightness level as moved and is at the maximum for no reason. I have uncheck the automaticly adsjust brithness and the rue tone opreferences. I have as well some screen (on the MBP) flickering issues some time to time. It seams that is a recurent problem since the MBP 2018. What are the solutions? No one seams to be able to fix those. On computers that cost more than 4000€ it's unaceptable, even if those MAC were cheapers it's not acceptable at all. Please find solutions, I been chasing Apple to solve those isues and till now, nothing.

Cheers

Same here!

I have macbook pro 2019 with external 4k display, after each AFK (5 min) unlock screen and brightness up to max and I need to set it manually back (I have "automatically adjust brightness" enabled) I'm using direct USB type-c cable connected

Hi, mine is not 5 minutes after, it depends, it might take 1 or 2 days. But i got "automatically adjust brightness" disable, you should try that, it's enabled by default. By the way do you have some screen flikering prob some time to time as well?

Same issue here on 16" MBP. Not a huge issue, but annoying. Basically every time I plug in my CalDigit TS3+ dock and open the lid, my brightness is set to max. Doesn't matter if "auto adjust brightness" is on or off. I do have FileVault enabled, so may have something to do with something in the pre-boot environment but not sure.

Same problem here! Running Catalina 10.15.1. on a Mac Book Pro, connected to an LG Ultrafine external monitor. I would set the monitor to the desired brightness level, put the Mac Book to sleep overnight and the next morning the display brightness is cranked up to the max. Sometime it happens within a few hours. Definitely a bug.

Hello. I have been having this same issue since updating to Catalina. I use two external LG 5K displays purchased from Apple, attached via two separate TB3 connections to a 2016 MBP. A few times per day I connect and disconnect the external displays, switching back and forth between using the built-in display vs. the two externals with the built-in display closed. Usually (maybe even always) when switching back and forth between the externals and built-in display the brightness of the displays resets to 100%. Both external displays get reset to 100% and must be manually adjusted back to my preferred level. Also the built-in display gets reset to 100% sometimes.

As other people have said, this is a tolerable but annoying bug. It can be adjusted back to correct levels fairly easy but I have to do this multiple times per day for multiple displays which has gotten old already.

A few people have mentioned a flicker issue. For at least a year I sometimes get a flicker when initially switching to the external displays. It's very obvious because I have two identical displays side by side and one of them will come on with a flicker, as if refresh rate is too low, while the nearby display looks normal and flicker free. Sometimes this clears itself with time, sometimes I clear it by unplugging and reconnecting that display. Note that I have not yet seen the flicker issue since upgrading to Catalina and I don't think I'd seen it for some months previously while a year ago it was frequent. So maybe this flicker bug has been fixed?