loud fan after power failure

What do you mean back to back?

Shutdown, unplug, wait 15 seconds, plug back in, wait 10 seconds and restart. Is this correct, it’s an Intel iMac?

Do I then start the iMac then shut it down when it gets to the login screen, and then repeat the rest of the procedure two more times?

Just making sure . I’ve reset SMC and NVRAM. I’ve reset the SMC a couple times but not back to back.

Thank you for your quick response. The back-to-back question wasn’t the intent, or entirety, of my reply. I wanted to be certain that I was clear what to do.

I reset the SMC three consecutive times. The fans still came on. Any other suggestions?

I also ran “Apple Diagnostics” it returned no errors. Also ran Disk Utility, same results, no errors. I had also zapped the NVRAM previously.

The problem started after three or so successive brownouts, lasting a few seconds each, just before a complete outage. The computer was connected to an UPS, and remained on. No one was at the computer while all of this was going on, so we aren’t certain if the UPS clamped during the brown outs. I assume it did as it was in the same state when last used. My wife says the fans were running loud when she safely shut down the computer. She never heard the fans running at all since buying the computer until now.

Okay, problem was with Safari. I trashed the Safari container file. So far, no more loud fans. The down side was restoring Safari preferences.