El Capitan does not detect my external display

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El Capitan does not detect my external display

I am working on a desktop iMac (Retina 5k, 27-inch, Late 2015) running OS El Capitan 10.11.6. On an average of about once every two weeks, upon startup, the Mac will not recognize or run the external display. Resetting the SMC did not help. After another restart, the cursor is frozen making login impossible. Upon a third restart, it asked me to reset my password. I did this and it disabled File Vault. Upon the next restart, all was functioning normally including the external display. Eventually, I have to re-enable File Vault.

This problem seems to occur randomly and without any logical cause. It is a minor annoyance, but one that takes valuable time to remedy. Apple needs to resolve this now with a bug fix. If anyone knows a workaround, please let me know. Thanks!

Posted on Sep 29, 2016 7:49 AM

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Answer 1

JayB.

Community Specialist

Sep 30, 2016 11:14 AM in response to DesignJack57

Hi DesignJack57,

I understand that your external display is not being detected right away by your iMac. Excellent way to troubleshoot the issue on your own. If you have not done so already, you can try resetting the NVRAM.

What is NVRAM?
A small amount of your computer’s memory, called “non-volatile random-access memory” or NVRAM, stores certain settings in a location that OS X can access quickly. The settings that are stored in NVRAM depend on the type of Mac you're using, and the types of devices connected to it.
Information stored in NVRAM can include:
Speaker volume
Screen resolution
Startup disk selection
Recent kernel panic information, if any

How to Reset NVRAM on your Mac

You may also want to upgrade to the latest and greatest Mac OS Sierra! macOS Sierra

Thanks for using Apple Support Communities to post your question. This should have your external display working with your Mac as expected. Have a nice day.

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