Chosen Solution

Just installed an SSD and 16GB of RAM in my 2013 iMac 21.5” w/IRIS graphics. Running fine and installed Bootcamp with Windows 8.1 for games. After installing a bunch of MS stuff, my display decided to go out. Meaning the image tears across the screen. Nuked the entire system and installed a fresh copy of macOS High Sierra. Picture and Big images come up but the screen still tears (see picture below)

After looking through the web and doing a test of Command F2 to another Mac as a second display, the image is fine on the other display. Conclusion is that the glass display is bad? I’m assuming that using a remote display uses the iMac graphics card (an Intel IRIS 1435, to power the 2nd display?). If so then the iMac glass is bad, right? If correct then the question is can I replace the iMac 2013 with the glass (meaning the complete glass module, with a 2009 Duo 21.5” glass mod. The specs look the same but not really sure of the pin-out and internal specs. (I’ve got a duo in the back room collecting dust). If not then how about a 2011 mid 21.5” model. I’m still using it as my ‘go to’ Mac.

Using remote access screen sharing doesn’t use the internal display it drives the video signal to the other system. While a useful diagnostic, it doesn’t fully check the GPU logic if you had a discreet GPU (AMD/NVIDEA). This series is a bit odd! As you can get it with only the Intel Iris Pro 5200 or with the addition of a NVIDIA GeForce GT 750M discreet GPU. So you really need to test it using either a DisplayPort or Thunderbolt display. Or, use a HDMI/VGA dongle. So you are sure your display is the issue Vs the onboard GPU logic. So that then leaves the question if you need a new display can you salvage your older display? Sadly no, The older displays are using a different signaling standard LVDS, from 2012 onward iDP/eDP signaling. While the connections look the same the pin assignments and the expected signals are very different. Think of it like having two bottles of a clear liquid in front of you one water and other Vodka (Sake)! Both are clear which one would you give to your kid to drink? You have a 50-50 chance fo getting it right, but the wrong could be very dangerous! While the Raw LCD panel: LM215WF3 (SD)(D1), LM215WF3 (SD)(D3) maybe the same, the problem is the LCD is hardwired (bonded) to the T-CON board as you can see here and not something you can switch out. Here your T-CON board is likely bad.

So here’s the needed display 21.5” iMac Display Assembly, Apple P/N 661-7109