When Should Fans Speed Up?

[Jthall502]

I have a new Imac 27" and was encoding a Video using HandBrake. I decided to check my temps using Temperature Guage app. It said My average CPU was 89 C but my average fan speed was still around 1100rpm..

Is this normal, at what point will the fans kick it up a notch?

 

[jav6454]

If you see CPU temps soar and the fans don't kick in, then check two things first.

1. Fan sensors
2. Fan air output

If either of those doesn't match, then you may have faulty thermal regulation and prolonged heating may cause damage.

 

[Jthall502]

So should my fans have been running faster at those temps?

 

[jav6454]

Theoretically, yes they should. 87*C is quite high.

 

[GGJstudios]

It wouldn't hurt to try resetting the SMC. However, fans may not spin faster unless sufficiently high temps are sustained for a period of time. The ambient temp of the room plays a role, as well. It's common for fans not to spin faster on temporary spikes in temperature.

 

[snapdragonx]

My imac is the same, I can encode video for 10 minutes and the fans don't kick in at all (past the default speed). Those CPUs are good for 105 degrees, but I personally don't like it getting that hot so I use an app to control the fan speed.

 

[Intell]

Also don't forget it's very, very common for the fans in a aluminum iMac to never spin up from their idle speed unless there is a hardware fault.

 

[WilliamG]

I've found the fan more likely to spin up under GPU load than CPU load.