I'm having a very strange issue. I inherited an Acer monitor from a friend that is full HD, 1080p. Good monitor overall. When connecting ONLY an HDMI cable from my Mac to the monitor, I get no signal. But if I connect both an HDMI and a VGA (via Thunderbolt adapter) to the Acer, I'm then able to toggle between inputs, and the HDMI input works fine. Problem is, now I have a useless Thunderbolt cable taking up one of my inputs. Any ideas?

MacBook Pro 15" Retina 2013

Yosemite 10.10.4

NVIDIA GeForce GT 750M 2048 MB

Acer S240hl monitor

  • Does the HDMI still work if you try unplugging the VGA while leaving the HDMI plugged in?
    – bjbk
    Aug 3, 2015 at 17:32
  • Also, try Detect Displays button in the Display pane of Displays preferences
    – bjbk
    Aug 3, 2015 at 17:36
  • No, once I unplug the VGA cable, the monitor goes black. Since it's a computer monitor and not a TV, I'm unable to cycle between inputs when it's black.
    – Cody
    Aug 4, 2015 at 15:49
  • Ah, I forgot, you have to hold the option key in order to see some of the extra features. Well, hitting Detect Displays did not help any. If I just had a third Thunderbolt port I wouldn't even care...
    – Cody
    Aug 4, 2015 at 15:58
  • FWIW, I have another HDTV that I used to use as a monitor before getting this Acer. It's a 19" Dynex. That used to be fine using HDMI from my old MacBook Pro, a 13" from 2009. If I try to use HDMI with my new 15" Mac, the same thing happens. No love from the HDMI slot... While VGA works perfectly fine. This leads me to believe it's something from the Mac, and not from the monitor.
    – Cody
    Aug 4, 2015 at 15:59


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