Try resetting the SMC Resetting the System Management Controller (SMC) on your Mac - Apple Support

You may need to do it 2-3 times and when you disconnect the power cord do it at the back of the mac not the wall.

I have the same problem with my iMac 21.5 late 2013. I reset the SMC and the PRAM many times but the problem continues. Please help!!!!!!

see very interesting     

iMac late 2013 OSX El Capitan - Fans Blazing on Boot

posted january 21

in case the post is hard to find, here's the solution proposed:

This solved my question Solvedby Shrooblord on Jan 19, 2016 12:18 PM

Yes, I tried that already.

However, there was definitely something wrong with the SMC. I looked at System Information (in Applications > Utilities) and found that the SMC firmware version was denoted 0.000. That seemed very strange.

I looked around on the Apple support website and ended up on this webpage
About EFI and SMC firmware updates for Intel-based Mac computers - Apple Support

where you can download firmware for various Mac models and their SMCs. Look under iMac Late 2013 and under the SMC Version column to get your firmware download.

After installing the firmware (this took literally 2 minutes), the fans stopped immediately. I put my ear close to the fans and you can hear them whirring very silently again. So they're back to normal operational parameters! Success!

So it seemed somehow during the installation of OS X El Capitan my SMC firmware got wiped, or corrupted, or flushed, or in any case made unusable. Downloading the firmware again from Apple Support was the solution!

Thanks for taking time to look into the problem guys,

Shrooblord

THANKS TO YOU SHROOBLORD  !

the firmware of my SMC is the latest

Why are you two hijacking this thread? You should start your own where you can be helped without cluttering up this one.

I talk about the same issue of csjohnson so I don't want to duplicate this one. Thanks for your comprehension

Hey mike,

1-my post was addressed at csjohnson

2-this is a forum, remember ? Not a chatroom...

what "clutters" a forum is the same problem chasing answers in multiple threads !

clodo9 wrote:

 

Hey mike,

1-my post was addressed at csjohnson

2-this is a forum, remember ? Not a chatroom...

 

what "clutters" a forum is the same problem chasing answers in multiple threads !

I know who you were responding to.

This is a forum and what you are doing is considered "threadjacking" and is considered bad form.

What "clutters" a thread is people hijacking with unnecessary me too posts and the replies they get. You don't know that the OP has a 2013 iMac therefore your reply to the second poster is off topic and not helpful to the OP at all. If the second poster had started his own thread you're right on point with your answer.

Sorry Mike but you are not help us, just let to other people help with their answers.

I'm not trying to help you. Good luck.

Thanks for your comprehension

was wondering if someone could easily access the thread i referred to up there. Checked : copy the "iMac late 2013 OSX El Capitan etc etc " up there and simply paste it in the "question" of the Apple Support Communities opening page. Click on the "we found similar question " ( not on the "submit question" )

hey sergio,

is the problem still there ?