I've just installed a new SSD in my mid 2010 27" iMac. I put it in place of the disk drive (ODD) so now there is no optical disc drive in my computer. After I did the installation I noticed that the fan speed shot up to ~3000 rpm and stayed there. So I downloaded SSD Fan Control and I'm currently using it to keep my ODD fan speed at ~1000 rpm. The system is running fine (from what I can see) and the noise it down to a minimum.

What I want to know is are there any dangers in doing this? The SSD isn't going to generate much heat at all but if there anything else around that part of the iMac that will generate enough heat to warrant letting the machine set the fan speed?

I'm assuming that this change in fan speed has happened because there isn't a signal being sent to the ODD temp input in the machine (since I've taken the ODD and thus the thermometer out, so it's defaulting to the highest rpm possible.


1 Answer 1


So, just to be clear, you replaced the optical drive in your iMac with an SSD and I am assuming a drive caddy.

In the process, you removed the optical drive temperature sensor:

iMac Optical Drive Sensor

When this sensor is absent, the fans will spin up to full speed. This is the "fail safe." So, you are using a software utility to control the fan and essentially override the systems ability to regulate temperature.

I would try to find a way to put that sensor on your drive to better control the fan speeds as the chips themselves would heat up under heavy use. Kapton tape should work just fine.

Damage? I don't know because I never removed this sensor and I am unwilling to experiment.

  • Yes, I've now got an SSD where my ODD used to be. I didn't use a caddy. I followed this guide which suggests tacking (with foam stickies) the SSD onto the chassis of the iMac. Due to the size of the SATA cable coming off the SSD I wasn't able to then reinstall the ODD like they do in the video (my iMac is of a slightly different version). I'll take a look into getting an SSD sensor, or maybe just a temperature sensor that can sit inside that portion of the case.
    – reelyard
    Sep 2, 2015 at 8:17
  • I've discovered that the sensor on the ODD is sudo-removable (it's stuck on the back of the drive near the SATA ports with a sticky foam pad, but I'm able to take it off). I'll try and remove that and attach it to the SSD in the same location (near the SATA ports).
    – reelyard
    Sep 2, 2015 at 8:30
  • 1
    Good to hear. Once you have that sensor put back on, your fan should work as intended.
    – Allan
    Sep 2, 2015 at 23:05

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