Amazon.com: DBTLAP Laptop CPU Fan Compatible for Apple iMac A1312 27" Hard Disk Drive 610-0041 069-3744 922-9152 Compatible for Delta BFB0612HB-HM01 HDD Cooling : Electronics
Further Explained: Apple's iMac 2011 Model Hard Drive 'Restrictions'
Apple iMac 27" A1312 Late 2009 HDD Hard Drive Cooling Fan 610-0041 BFB0612HB 640746726392 | eBay
Apple iMac A1225 2008 24" Genuine Hard Drive Cooling Fan Center 620-4336 for sale online | eBay
Intel iMac 24" Hard Drive Fan
OWC In-Line Digital Thermal Sensor HDD Upgrade Cable for iMac 2011
Amazon.com: 620-4324 922-8510 iMac 20inch A1224 Hard Drive Fan : Electronics
iMac Intel 21.5" EMC 2428 Hard Drive Fan Replacement - iFixit Repair Guide
iMac Intel 21.5" EMC 2428 Hard Drive Fan Replacement - iFixit Repair Guide
Cleaning iMac fans | MacRumors Forums
Needed to make a mid-2011 iMac HDD fan shut up, while using a replacement drive. Used a couple of resistors to approximate a thermal diode constantly at 37 degrees C. : r/techsupportmacgyver