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Mike, Mac Medic
Category: Mac
Satisfied Customers: 8911
Experience:  Over 20 years IT experience with Apple computers in publishing, marketing and design.
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I installed EL CAPITAN OS X and now I can't see my dual

Customer Question

I installed EL CAPITAN OS X and now I can't see my dual monitor. Its connected as before and has power but says "NO SIGNAL"...
Submitted: 1 year ago.
Category: Mac
Expert:  Viet - Mac Tech replied 1 year ago.


Please try the following:

  1. Go to the Apple logo / menu, then choose System Preferences
  2. Open Displays
  3. Press and hold down the Option key on the keyboard, and it should show the Detect Displays button.
  4. Click on the Detect Displays while holding down Option to use the function.
  5. Then adjust the displays settings there.

More info:

Please let me know. Thank you.

Customer: replied 1 year ago.
Hi Thank you for your information I read the two links as well. However, this doesn't seem to be working. My display is not being detected. And up until I installed El Capitan it worked fine. So I don't think its hardware related.
Any other suggestions?
Expert:  Viet - Mac Tech replied 1 year ago.

Sorry, can you make sure all updates get installed?

Can you click on the Apple logo / menu, then About this Mac, then More Info, then Hardware, Graphics/Display, and let me know the graphics model there. Thank you.

Customer: replied 1 year ago.
Viet, I always have all my updates installed. I have 8 Apple products and they are always up to date with the latest OS and updates...I'm very meticulous about this. But this happened to me AFTER I installed EL CAPITAN. I have no issue with this when I was running Mavericks or any rate, I've attached the photo of the Display/Graphic. Are you a Mac Expert? I only see your credentials with Windows...
Expert:  Viet - Mac Tech replied 1 year ago.

Yes, I am; I support windows and mac and iPad, etc. I'm sorry, but I'm not sure about this monitor issue with El Capitan, so let me open the issue to other experts. Thank you.

Expert:  Mike replied 1 year ago.

What model display is it and what port on the iMac is it connected to?

1. Shut down the computer.

2. Unplug the computer's power cord.

3. Wait fifteen seconds.

4. Attach the computer's power cord.

5. Wait five seconds, then press the power button to turn on the computer.

6. Press and hold the Command-Option-P-R keys before the gray screen appears.

7. Hold the keys down until the computer restarts.

8. Release the keys.

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