Chosen Solution
Hello, The screen on my iMac 2013 broke, so I decided to remove it and use an external display. After removing the screen, the fans ran crazy high and it was under-clocked, which makes sense (I now know) because there’s a temp sensor in the display. My issue is when I plug the broken display back in, the fans are completely quiet, so the temp sensor is A-OK, however the mac now runs EXTREMELY laggy. I’m talking you move the mouse and a full two seconds later it jerks over. I haven’t even been able to log in when it’s like this, it just locks up. When I unplug the display it goes back to crazy fan and under-clocked-but-usable mode. Does anyone have any idea how to stop the mac from under-clocking when I have the display unplugged, or better yet, why it gets extremely laggy when I plug the display back in? Any help is greatly appreciated. Thanks, Sebastian Update (07/10/2018)
https://photos.app.goo.gl/6F65x4LX1wA3Nv… The first two are when I have the broken iMac display plugged in. When I have it like this, it’s SO ridiculously slow, like it took me forever to move the mouse and click on things, BUT the fans are silent as they should be. The second two photos are from when I then unplugged the iMac display from the iMac. It suddenly become very usable and the mouse is perfectly responsive (though still slightly underclocked), but the fans all go full blast. There’s one drawback to both, though with the first it’s basically unusable. No idea why this is happening when I have the display plugged in. PS, thanks for the reply! :)
Sounds like you’ve got a second problem here within SMC services as it still thinks there is a problem so its putting the CPU in failsafe mode which is when the clocking is reduced to a low clock rate. How about installing this app: TG Pro this will allow you to see all of the sensors and the fans. How about taking a snapshot of the main window (make sure all of the sensors are visible) and past it here for us to see Adding images to an existing question Update (07/13/2018) Well your display is damaged beyond hope here. Time for a new one! I suspect you damaged it in the process of taking it off. [linked product missing or disabled: IF173-047-1] and you’ll need the adhesive strips here: [linked product missing or disabled: IF173-005-1]
