Slim iMac having issues after hard drive replacement

[nighthawk01]

So a Late 2013 iMac I bought has been having quite severe issues. The hard drive has been replaced with a Toshiba hard drive, so the temperature sensor does not work correctly - therefore setting off the fans. This is corrected with the 'SSD Fan control' but the computer still runs terrible. Worse than a plastic MacBook that I have for comparison. The computer is indexing but that cannot equate to kernel_task taking a supposed 300% of the CPU! Not sure where to go next, as I got the computer at a steal and it is in overall excellent condition.
Thanks.

EDIT: After removing 'AppleSMCLMU.kext' as well as editing the 'IOPlatformPluginFamily.kext' the computer now functions perfectly.

 

[nambuccaheadsau]

Is this the 27" model? If so suggest a heat sensor kit from OWC.

For mine all artificial fan control software can lead to problems.

 

[nighthawk01]

Is this the 27" model? If so suggest a heat sensor kit from OWC.

For mine all artificial fan control software can lead to problems.

It's the 21.5, I'll think about getting the heat sensor kit but meanwhile the computer runs cool and quickly.

 

[nambuccaheadsau]

The 21.5" models do not need the kit as they went to 2.5" drives to overcome the problem in 2012.

 

[nighthawk01]

The 21.5" models do not need the kit as they went to 2.5" drives to overcome the problem in 2012.

So would it technically be impossible to replace a hard drive in a 21.5" natively without experiencing fan issues?

 

[iMacC2D]

Removed.

 

[nighthawk01]

One of the computer's internal electrical or thermal sensors is not reading, or is reading outside of spec. Whenever kernel_task uses an excessive percentage of the CPU time - and 300% is common - it's because the machine is throttling down as a failsafe.

It would need to have some kind of Apple diagnostic run on the machine to determine what sensor isn't working correctly, and then repaired based on whatever sensor or component fails the test.

From what I've heard the computer had its drive replaced and then it was completely cleaned. I can't see how a sensor would start malfunctioning - which leads me to believe the sensor is simply missing from the replacement, which was causing the computer to crank the fan up.

 

[iMacC2D]

Removed.

 

[nambuccaheadsau]

Just the opposite nighthawk simply replace the 2.5" hard drive and no problems if everything has been re-connected properly and no sensor kit needed. I think a sensor may well be unconnected or need tighter clipping together.