I used the iMac Opening Tool just as shown starting in step 2 to separate the tape. DISASTER! The screen cracked! I used the tool slowly and carefully and despite this, the screen cracked. I should have simply used a guitar pick. That said, I decided to see if I could upgrade the 8GB RAM to 16GB RAM WITHOUT removing the logic board all performing all of these steps. I found I could simply remove the FAN assembly as shown in step 43. This makes enough room to reach behind the logic board and unclip the 2 memory modules. I installed 2 8GB modules (1600MHz DDR3L SO-DIMM PC12800 204 Pin) without much trouble. I used a plastic stick to reach behind the logic board and unclip the existing memory modules, then carefully inserted the new ones and clipped them into place. This is much easier than performing all of these steps.

I used the iMac Opening Tool just as shown in this guide to separate the tape. DISASTER! The screen cracked! I used the tool slowly and carefully and despite this, the screen cracked. I should have simply used a guitar pick. That said, while I was inside my iMac replacing the Harddisk with a SSD, which was pretty easy to do, I decided to also see if I could replaced the 8GB RAM with 16GB RAM WITHOUT removing the logic board, as shown in other instructions on this site. I found that by simply removing the fan assembly, this makes enough room to reach behind the logic board and unclip the 2 memory modules. I installed 2 8GB modules (1600MHz DDR3L SO-DIMM PC12800 204 Pin) without much trouble. I used a plastic stick to reach behind the logic board and unclip the existing memory modules, then carefully inserted the new ones and clipped them into place. This is much easier than removing the power supply and logic board and all of the associated connectors and screws.