After updating to High Sierra on early 2011 MBP (with Samsung EVO 850 SSD), the screen is very dim (about half normal brightness) and the fans are constantly spinning. Machine is not getting hot or even warm, but fans are on non-stop. My first install failed and I needed to install via internet recovery mode. That seemed to work fine but the screen was dim. To fix dimness, I then did a NVRAM update (reboot while holding down CMD +Option +P +R), and after boot that's when I noticed the persistent fans. So now I have two problems. Any ideas?