Chosen Solution
I have a 2011 mac mini and went to do the second HD upgrade, and ever since the CPU fan is stuck at full speed. I have tried to reset PRAM and SMC but i cannot tell if they have actually reset, not sure if the sandy bridge based macs use something different. I also ran the “d” diag utility and everything passes. The machine runs fine the fan is just stuck at 100% and its very annoying.
It sounds like you may have a faulty sensor. Your unit should still be under warranty and I would take it to Apple and let them fix it for free. Just noticed you did a hard drive upgrade so Apple would probably not cover your problem. Please go over the steps in your upgrade and see if you missed a sensor.
The “missing” componet is the thermal sensor, which is attached to the stock hard drive. When you take the stock hard drive out you will see that there are two connectors - the main hard drive connector and another, thinner connector. The wires for that thinner connector are stuck to the side of the hard drive with the plastic “cover”. A cursory glance will make you think those wires are just part of the hard drive, some superfluous connector that it appears you don’t need, since the SSD works fine with just the main connector attached. They are not superfluous. And those wires don’t actually go into the hard drive either. If you have a look at step 21 of the Crucial SSD installation guide (http://guides.crucial.com/Guide/Mac+Mini…) you will see that the thermal sensor is just softly glued to the hard drive, probably because that’s the thing that would tend to get the hottest when the system is working hard. All you need to do is pull the plastic “cover” off and then gently peel off the sensor from the hard drive. Then you can plug the sensor back in to the appropriate socket on the main board and run the sensor to somewhere where it might get hot. I just ran mine up near the RAM and now my fan works correctly.
Kyle, One thing to check is the print manager. Sometimes the CPU gets stuck on trying to print to an unconnected printer. Go to Finder> Utilities> Activity Monitor Select display all processes Find the process taking up the most CPU % and kill that process. The fan speed should drop within seconds. Let us know. Frank
I had this fan spin issue on my older core 2 duo mac mini, after installing an ssd. I solved this by replugging the fan in proper orientation. I must have turned it around during reinstallation. Possibly this is a solution here also.
I have resolved my fan issue. A surface mount component had somehow come off the logic board and as a result the (pwm) fan control signal was not controlling the fan. The fan defaults to full speed when it sees no pwm signal. I was able to see the (monitor) signal was working by using smcfancontrol and the slowed the fan with my finger - the rpm changed. As a result the mac was requesting, for example, 2000rpm, but as the fan didn’t see the request it was giving approx. 6500rpm, hence the error code. The missing component was a bridging SMD device. By hooking up an oscilloscope I could see a pwm signal on one side of the missing bridge, but no signal at the fan. As soon as the 2 pads were bridged normal service resumed. Not sure how this component has become detached, presumably when I removed the fan connector. Anyway, it is worth checking for 2 solder pads just above the fan connector - if you see no component then you may have the same issue!
CREATE THIS ON AUTOMATOR /applications/smcfancontrol.app/Contents/resources/smc -k F1Mx -w 1770
I downloaded a fan control program from http://www.crystalidea.com/macs-fan-cont… and it has worked well so far. My problem when I pulled off a socket from my board when removing the plug attached to my optical drive thermal sensor while replacing the battery. The sensor program allowed me to choose among different sensors by listing their current operating temp and what component they were sensing.
Macmini 2012 with SMC Fan Control and iStat menu monitoring fan speed and temperatures and it locked into 5,500 rpm today and would not quit. I removed the plastic base while stilled plugged in and running and was shocked to find a thick layer of dust similar to the lint you’d find in a clothes dryer covering the perforated metal screen. I removed the dust by hand and sprayed the rest with compressed air and the fan speed dropped to normal immediately.
My 2010 Mac mini server fan speed 5xxx RPM is solved by swapping temp sensor soket between the 2 HD after a overheat shutdown problem and showed a exhaust reading error. Software fan control can help you diagnostic problem and temporary solved it by a fixed RPM, however it may damage your system while it is stopped to work and your system will be overheat w/o noticed fan is out of work. Also it would have occupied your CPU heavely, you should stop it(remove it from \Libary\App…) while you don’t need it. Try to fix temp sensor first while you have a noise fan.
I have a similar problem. The fan “revs” and then slows down. After about 9 seconds, it revs again. I tried a restart and that helped temporarily. Do I need to replace the fan?
Had the same issue after a SSD upgrade. I’m with osx30 on this one. It was simply the heat sensor connectors not seated properly on the logic board. I blame my aging near vision. Even with good reading glasses I couldn’t see it. But when I opened up the case again and used an OptiVisor and some good light, I could clearly see that one connector wasn’t snapped all the way in and one was actually inverted. Once those issues were corrected, the fans behaved normally. All I can say is look carefully at those connectors.
I have a similar issue on a Mac Mini 2010 server. In my situation, the fan runs high and the ethernet port doesn’t seem to work. For some reason, I can’t run any diagnostics on it. Most likely it is a motherboard issue.
