Chosen Solution
Hello community, i have a problem with a 15” MacBook Pro Mid 2014. I can only boot the macbook when a external monitor is connected and the lid is closed. If I try to start the macbook without a external monitor I hear the macbook chime, but only the backlight is working and nothing appears on the screen. I also tried to open the lid after I booted the device with the external monitor. But as soon as I open the lid the MacBook freezes. Maybe someone give me a tip to find a solution. Thank you. Update Here are the photos from the display connector and cable. In my opinion they look good.
Sounds like your internal display or its cable is damaged. Take the bottom cover off and inspect the display cables connection on the right side do you see any corrosion or physical damage?
Heres the IFIXIT guide to pull the bottom cover off MacBook Pro 15" Retina Display Mid 2014 Lower Case Replacement Update (12/04/2018) @blob810 - Did you check the display cable connection? I’ve seen a few with corrosion which shorted out the data lines which then causes the system to freeze up. After disconnecting the battery disconnect the cable and then re-power the logic board with an external display does opening the lid mess up the display? If it does then @benjamen50 is correct your Hall Sensor logic is messed up. The location of the sensor is located on the backside of the logic board.
You’ll need to check for corrosion damage on that side of the logic board once you take it out MacBook Pro 15" Retina Display Mid 2014 Logic Board Replacement
