Optical Drive fan fast
Original problem was that the DVD drive wasn't recognized (no drive, and no power to drive).
Took iMac apart, and repalced it. Still didn't recognize new drive. Took it apart again, and put in original drive.
Still didn't recognize it. Cable is plugged in. New problem: ODD fan is running at full speed.
Reset SMC. Reset PRAM, to no avail. Finally just unplugged it, since the ODD 'didn't work' anyway. left it like that for a year or more. Computer works, but will lock up hard once pretty often, usally after waking from sleep.
Tried to look again. LCD sensor is connected fine. All other cables are connected fine. ODD drive works! like magic!
Ran Apple Hardware Test from DVD. It says HDD! fan is problem, and running at 1380 RPM. (1100-1200 is idle) Took HDD fan out. Looks fine, everything is connected. UNplugged ODD fan, ran test. Says ODD fan problem, 0 RPM.
Installed various programs to OS X, 10.9. All say temperature sensors are within spec. Some note ODD fan way over idle speed. Nothing noted about HDD fan.
Interestingly! and here is the question I guess. None mention ODD sensor! THey don't list it at 0, or out of spec, just NONE at all.
So, might this be indicitive of bad ODD temp sensor, that I broke with adding and removing ODDs?
Is this a good question?