Machine Type: iMac Intel or G5
Symptom: Fans are always running (come on more often) after a hard drive upgrade or service.
Likely Cause: Temperature sensors were not reseated properly.
The temperature sensors help tell the computer when to turn the fans on and what speed they run.
On the iMac, there are temp sensors over the optical and hard drive. If these sensors aren’t secured properly in the right position to a new drive, the readings may not be accurate causing the fans to come on when they shouldn’t.
Since the temp sensors are originally applied using sticky glue, they should be secured back into place when installing a new hard drive or optical.
We’ve seen a lot of cases of iMacs coming in with the fans always on after someone (not MyService) installed a new hard drive. The temp sensor was usually in the wrong place or had come loose inside the case.
If you’ve done a DIY upgrade, make sure to check the temp sensors first if you are experiencing any fan issues.