iMac Core i3 mid 2010 hard drive removal and fan control I'm thinking of adding an SSD.  I'm getting conflicting advice as to what to do with the sensor cable if swapping the mechanical drive for an SSD.

I think in these units, there is a sensor cable that runs to the mechanical drive, rather than a sensor probe stuck on the drive.

I've read that some short this cable, some put a resistor on it, even some saying mover the sensor from the optical to here.  I have no idea if that is sound advice or not.

So it made me think, if I just do away with the mechanical drive entirely and unplug the sensor cable.  And swap out the optical for an SSD.  Will the iMac boot fine with this arrangement.  And will it be smart enough to realise that there is no HDD plugged into, let's say the main slot, and therefore not care about fan control at all for that drive?

For context, apparently if the sensor cable is not tackled, the fans roar at 100% for this model and similar setups, when doing a swap of the mechanical for an SSD.
The usual result of removing the thermal sensor is roaring fans; I suspect that there's little reason for Apple to add some "if no drive, ignore sensor" logic, because Apple would want to replace the drive.

The best instructions for replacing components on your Mac can be found here:
https://www.ifixit.com/Search?query=imac%202010

Remember that your iMac has a SATA II (3 Gbps) controller, so you're not going to see the full benefit of the SSD: though it will probably double your HDD's speed.

If your iMac had Thunderbolt, then I would have said avoid the hassle and use an external drive; but it is a 10-year-old Mac!