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