Macbook Pro (Mid 2012) screen is just white no picture I swapped out my broken unibody display assembly with another and now the new screen is just white (backlight is working) but nothing else. External monitor is working just great though, so I am forced to use it this way. Any ideas about why it's just backlight working?
I put the old assembly back in and it's totally black, but the external monitor still works just fine.

Thank you, in advance. I appreciate any ideas or solution.

MacBook Pro (13-inch, Mid 2012)
Model Identifier:   MacBookPro9,2
Processor Name: Intel Core i5
Processor Speed:    2.5 GHz
Number of Processors:   1
Total Number of Cores:  2
L2 Cache (per Core):    256 KB
L3 Cache:   3 MB
Memory: 8 GB
Boot ROM Version:   MBP91.00D3.B0B
SMC Version (system):   2.2f44




Chipset Model:  Intel HD Graphics 4000
Type:   GPU
Bus:    Built-In
VRAM (Dynamic, Max):    1024 MB
Vendor: Intel (0x8086)
Device ID:  0x0166
Revision ID:    0x0009
Displays:
 Display:
  Resolution:   1152 x 870 @ 75 Hz
  Pixel Depth:  32-Bit Color (ARGB8888)
  Mirror:   Off
  Online:   Yes
  Built-In: Yes

 Acer AL2216W:
  Resolution:   1680 x 1050 @ 60 Hz
  Pixel Depth:  32-Bit Color (ARGB8888)
  Display Serial Number:    ETL7409038   
  Main Display: Yes
  Mirror:   Off
  Online:   Yes
  Rotation: Supported
That is a tough one. the Mac sees that there is a display there and even has it's resolution and other specs. So the OS sees and enumerates it, yet only the back light is on.

That may indicate that there is an issue with the replacement display, or that something was damaged or not installed correctly (crossed, damaged wire/conductor/connector).

You are troubleshooting hardware and there is not much else to do than go through the install procedure and verify that everything is connected properly. In other words, remove and reinstall.

Also do you know for a fact that the replacement display is both the exactly correct one and that it is, itself, working properly? It is also entirely possible that you got a defective replacement display.

I would imagine that doing it yourself means that you would either rather not send it off for repair or can't afford that option. If so it may be time to look into that latter option...