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Model A1419 / EMC 2806 / Late 2014 or Mid 2015. 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (ID iMac15,1); EMC 2834 late 2015 / 3.3 or 3.5 GHz Core i5 or 4.0 GHz Core i7 (iMac17,1) All with Retina 5K displays

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How to disable/trick/bypass the LCD temperature sensor..?

I have disconnected internal 5k display and have connected that to a circuit board allowing for external inputs (I can now use the 5k screen as external monitor with my new laptop)

I would still like to be able to use iMac as a computer - it will boot with external screen (even its own original screen connected “externally”) but the fan spins full speed and the CPU throttles… I assume this is because there was a temperature sensor on the LCD panel which is now not connected to iMac meaning iMac thinks its overheating…

Is there anyway to make the iMac ignore that sensor? slowing the fan will presumably not stop the CPU throttling… the sensor was connected through the iDP cable so there are a lot of very small pins and don’t fancy trying to short the sensor.

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Apple uses a newer interface standard striking from LVDS to iDP.

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What you are asking is not really practical or safe!

The system was not designed to run without a display present as it controls the air flow internally as well as protect you from high voltages from the power supply.

The GPU logic is not designed to run without the internal displays load, you will damage your system running it in this state.

I would strongly recommend you get a replacement display for your iMac or put the original one back in.

Update (01/16/2021)

Maybe this will help you.

I’m sitting on my couch watching TV using a 15” 2012 MacBook Pro. I have a small project running on my MacPro in my study as it takes about an hour to run I can watch things remotely connecting to it.

This is a better method than trying to wire in your second system into your iMac so you can access your second systems video feed.

I don’t recommend Rube Goldberg machine builds when simpler methods are available.

If you want to have a iMac like display why don’t you look for a junker which you can convert into a display. You have the needed kit already so all you need is a case, power supply and a good display!

Then you can have a matching unit besides your current iMac! You could even use it as a second display to your iMac via a mDP cable connection.

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Thanks for the info...

I will be putting the display back onto the iMac with the extra circuit board that allows for the external inputs in the space where the fusion HD would have gone if I had one and the DisplayPort cables out of a new hole in the back...

As for the GPU logic, I did not know it couldn't run without internal display so thanks for that - Am I correct to assume the load of a screen output on the thunderbolt port is not adequate load? If so is it possible to get an iDP to DisplayPort (or two) cable?

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I’d also like to achieve the same thing. We had a customer drop his 5k Display 27” and decide to replace the entire computer rather than the screen. I now have an upgraded 2015 27” I’d like to use as a desktop (put into a case). I’m experiencing the same dirt-slow throttling. Macs Fan Control or TG Pro will manage the fan speeds, but the only solution I’m aware of is to use the board/sensors from a screen to trick the machine into thinking there’s a screen attached. Let me know if anyone finds a fix to this, as this machine would be a great desktop computer for my purposes if I could just get around the CPU throttling. Thanks!

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To Caldwell Wagenheim, just use the iMac with the broken screen still connected with an external monitor, or just install Ubuntu Server with a monitor connected use it as a server of some sort.

That iMac would make an amazing Minecraft server!

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I have 2 LCD panels from old iMac computers.

You can buy working LCDs from computers that are no longer with us online for pretty cheap.

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Hey I am doing the same thing and I just found a fix to this :)) (I know this reply is late but I just wanted to see if you still want a fix to this issue)

https://github.com/calasanmarko/TurboMac

It fixed the thermal throttling issue on my 2017 27’ iMac, and I’m using Macs Fan Control to keep the fan down and it’s as good as if the temperature sensor was stilll connected!

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Hi there! i've been thinking of doing the same thing as I'd like to convert my 5k imac into a display but keep the guts around for bootcamp/other stuff. Just to clarify, Turbomac allowed you to book the imac guts like normal/no safemode throttling without the internal display connected? That sounds like a dream lol

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@heatherlegere - This systems GPU is not that good for rendering video or image work. Review what people do for mining Bitcoin! You can pickup an older system quite cheaply, or a few to make a rendering bank.

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