Solved Replaced Hdd With Ssd Fan Keeps Running No Boot Imac Intel 27 Emc 2546

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Finished replacing the WD HDD in my Late 2012 iMac with a Crucial 1Tb SSD. I THINK I reassembled everything correctly but when I powered up I got the chime but nothing else except a running fan at full tilt and a black screen. I replaced the drive because I only got a partial boot before the system powered down. I took it to an Apple Genius who determined the original HHD was dead, not spinning. I reset the display power and data cables securely. Any thoughts on what I can do to wake this thing up?

Switching out the HDD for a SSD is a great way to get the most bang out of your system! But… You need to replace the HDD’s thermal sensor for the systems thermal management to work properly iMac Intel 21.5" and 27" (Late 2012-Late 2015) SSD Temperature Sensor which is why your systems fan is running hard. But you also have a second issue here with the display, did you follow this guide to the letter? iMac Intel 27" EMC 2546 Display Replacement or this one iMac Intel 27" EMC 2546 Hard Drive Replacement as you can damage the display if you don’t use the correct tools and technique as outlined. If you have access to an external display see if it is working, hopefully its just a cable issue. Once you get the display issue resolved you should then be able to install a fresh OS using Internet recovery following this Apple TN How to reinstall macOS

HiYa, Black screen and fans running full at boot means that you have not plugged in the LVDS cable properly (No video getting to screen and the thermal sensor of the screen is not being seen and so fans run at full).. Re-seat the cable (the ribbon style one with the latch) and it should come back (unless you have damaged the cable in which case it may need replacing). I have replaced many (MANY) hard drives in 2012-2019 iMacs and only seen 2 which needed the thermal sensor - in both cases the fan was running a few 100 rpm faster than the stock setup and being used in a very quiet environment - cottage on a hill style and acoustic music studio) - most people don’t even hear the difference.