Blue screen of death, high fan speed, questionable graphics.

Hi,

My Imac had some issues in that the Activity Monitor was always blank and it slowed down significantly more and more when downloading using Google Chrome.

One day it got very hot then presented a blue screen and crashed.

I took it apart and redid the heat paste on the processor and GPU as well as cleaning out all the radiators and fans.

I broke the screen connection lead on replacing it and don’t really want to buy a new one until I know the iMac is recoverable.

It starts with no screen on just fine but the fans are now coming on full blast as soon as the operating system kicks in. Only the ODD fan and the processor fan, the HDD fan is on but running quietly.

Also the external screen (that I’ve checked does work with other Macs) is jittery, especially when using chrome.

I’ve done a full hardware check and it said the LCD temp sensor was the only item that was faulty so I refitted the screen fittings (aside from the broken lead) and the issues remain the same.

It will only boot in safe mode, I have replaced the inner battery, reset the Pram, booted it off of 3 different hard drives, each with different versions of the operating system on and the problems remain the same.

I have also unplugged each temperature sensor one by one but it always reacts the same. I have 4 RAM slots, all in use, I have tested by using two at a time with different sets of RAM, no difference.

Processor works, it loads in safe mode, I can play videos, I have tried 3 Hard disks, I have tested RAM, I have reset PRAM, the heat paste is reset on the processor and the graphics card.

Does anybody know if the screen being off/disconnected causes this reaction?