Solved Internal Display Only Works When An External Display Is Connected Macbook Pro 13 Retina Display Early 2015
Chosen Solution the internal display only works when a external via HDMI is connected, at that time both internal and external work perfectly, disconnect external and nothing but garbled horizontal lines, replaced logic board and display with no positive result still same symptoms It was the LCD after all , I originally tried what was supposed to be a known Good lcd and then was unsure after symptoms did not change....