Mac Mini Unibody

A unibody aluminum generation of the Mac Mini identifiable by the model number A1347, spanning the Mid 2010 to the currently sold Late 2012 model.

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Fan is stuck on high speed, ODD heat sensor pulled off motherboard

While swapping a hard drive, I broke the optical drive heat sensor socket from the logic board at four tiny solder points. I wish I'd found ifixit.com first, because their procedure avoids detaching the optical drive heat sensor. I attempted to use non-permanent glue to bring the socket into contact with the raised solder bumps on the logic board, but that didn't work. So I removed the glue and put a small piece of electrical tape around the optical drive SATA connector (so that the cowling would not seat the SATA connecter when reassembled) and I reassembled the Mini with the new drive in place. When I completed the installation and started the Mini, the fan immediately came on at full speed.

SMCFanControl indicates 5500 rpm and a temp of 31 degrees C. System Profiler indicates that the system recognizes that there is NO optical drive. I reopened the Mini and checked that all of the remaining connectors were properly seated. iStat Pro indicates that the heat sensors for all other components are operating correctly and reporting temps between 23C (ambient) and 32C (CPU). Apple Hardware Test reports error code 4SNS/1/c0000008: T00P--124, which I interpret as an error related to the optical drive heat sensor.

The Mac Mini functions perfectly in all respects except the constant fan at 5500 rpm and I have no optical drive. The Scorpio Blue is much more responsive, everything works and I spend much less time waiting for the spinning beach ball to complete tasks. Third party fan controllers are useless, as they will not lower the fan speed. Putting the computer to sleep from the Apple menu shuts the fan down completely. Wakeup restarts the fan immediately.

I've performed the correct sequence for SMC reset, which did not help (SMC Version system is 1.65f2). I've booted into SAFE mode, then restarted normally, which did not help. I've performed a PRAM reset through five startup chimes, no luck. The Mac Mini firmware is up-to-date. I do not have sufficient soldering skill to reattach the heat sensor connector to the motherboard (there are two conducting pads and two more mounting pads within the space of 2 mm). Will the system think that the optical drive heat sensor is present if I connect (short) the two solder pads on the motherboard for the broken optical drive heat sensor? Will that solve the problem or kill the motherboard?

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There are a LOT of different things that can cause the fans to go full blast, but this time it boils down to you knowing you broke the sensor. The system either think(s) that something is overheating or broken. The system, not knowing the temperature, is running the fans overspeed. Your AHT error indicates that the TOOP fan is running out of spec by ~124,000RPM. AFAIK there is no software solution to this problem.

Jumping the connectors is not a good idea. ''Basically, the temperature is read from these sensors by taking measurements of their voltage outputs. The sensor is supposed to regulate the voltage - since it can't, 'cuz it's missing the "default program" or fail-safe for the OS not getting the proper feedback from the sensor is to keep on the fans. Mucking about intentionally shorting out parts of your logic board is not good DIY procedure, unless you do not care if you further destroy the board, because you're willing to replace it.''

You're not running from battery power - so aside from the noise your issue is something failing. IMHO It would cost less to replace a failed fan than a CPU or HD.

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Thanks, machead3. I'm no expert, which is why I'm asking for advice. Please understand that I'm taking the optical drive out of the loop by disconnecting the ODD SATA connector. I don't use the internal optical drive (I have an external optical drive because the Apple drive went funky and is too difficult to replace), and I have no need for the internal ODD heat sensor. The ODD heat sensor is broken off the logic board, thus the circuit is open and calling for maximum fan (5500 rpm reported by iStat Pro). Presumably the other extreme is circuit closed and calling for zero fan. Is this true? If so, please tell me what possible harm I can do by bridging the two solder pads to close the circuit for the ODD heat sensor? The hard drive heat sensor and the CPU heat sensor remain intact and fully functional.

by Enrico

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2 years later but still might come in handy.

SSD Fan Control for OS X is free and can bypass this.

http://exirion.net/ssdfanctrl/

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Enrico will be eternally grateful.

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