Ok so I have had my iMac for about 16 months and been happening a while now the fan never stops spinning at fast speed it gets quite noisy from before it even boots up I’ve googled and tried all the obvious troubleshooting, reset the smc numerous times make sure adequate ventilation and holes underneath aren’t blocked and as a last resort I even deleted Mac and reinstalled Mac OS but still the same so is there anything else I can try before I take it in to Apple... thanks