Mid-2007 Mac mini fan running fast after adding a hard drive

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Hello everyone,

I recently bought a Mid-2007 Mac mini from my university surplus store. The machine is a 1.83 GHZ Intel Core 2 Duo model with 2 GB Ram and came without a hard drive. When I first tested the computer without a drive, it was extremely quiet, but after I followed iFixit's guide to replace the hard drive and installed Lion, the fan is extremely loud. The high fan speeds continue while starting up, and the speed lowers when the computer is idling on the desktop. If I try and do anything such as use Safari or update the machine, the fan speed goes back up.

I have done research into this issue, and several people have stated that this is the result of not correctly plugging in the hard drive temperature cable. I have, however, ensured that the cable is properly installed. In addition, I know that the fan currently runs lower than if I start the computer with the cable completely unplugged (I have tested this). This leads me to think that the cable is indeed intact and properly connected.

The first hard drive I installed is a 2.5" that used to be in my Mid-2012 MacBook Pro before I upgraded it to an SSD. I then installed another I had lying around, and it produced the same issue. Additionally, I am currently running smcFanControl to keep the fan speeds off 5000 RPM, and have observed a temperature around 40-54 C. I have also already tried resetting the SMC (unplugged for 15 seconds, and plugged in for 5 before being powered on). On top of this, I have run an Apple Hardware Test that returned no errors. Besides the fan issues, the Mac mini is running extremely well.

Has anyone else encountered this problem when installing a new hard drive or have any ideas what could be happening to this mini? Should I ignore this and keep using smcFanControl to idle my computer or is there a fix? I'd much prefer having the computer take care of the tasks of temperature regulation; it's quite distracting having to do it myself.

Thanks in advance.
 

chscag

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It sounds like the temperature sensor cable is bad. That would drive the fan speed to maximum. Since it's an older unit, I would just continue to control the fans speeds using software unless you can get another temperature sensor cable and not pay too much.
 
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JollyRogerBay
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Thanks for the quick reply. The weird thing with this mini though is that the fan will eventually slow down to a reasonable 1500 or so RPM if I leave it idling at the desktop. When I open any applications or browse the internet with Safari, it will shoot back up to 3000-5000.

Would this still be a broken temperature sensor cable?
 

chscag

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Yes, I would think so. The sensor is probably old and not responding correctly although it's still working somewhat. You can't let the fan max out too many times because it will eventually wear out the bearings and then you'll need to replace the fan.
 
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In that case, I'll keep using smcFanControl. I've currently been using the command line controls to limit the maximum fan speed to around 2500-3000 RPM, and the program reports a temperature between the mid 40s to low 50s Celcius.

Is that a safe temperature and fan speed? Most of my Macs before this one are whisper quiet with just the minimum fan speed, and I'd like to have this one be as quiet as possible. Any suggestions?
 

chscag

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The temps are fine. As long as you keep monitoring the temps and don't do any wild gaming on that machine you should be OK. Keep in mind it's 7 years old going on 8. You don't want to put any large amounts of money into it. You can probably keep the fan speed at around 2000 RPM most of the time. That should be fairly quiet. Also, make sure you've cleaned out the chassis real good.
 
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2000 RPM is indeed nice and quiet in this machine, so I think I'll keep that in mind and let it hover around there. I've also taken the computer apart several times, and I can confirm that the chassis is very clean.

Thank you for your help and advice! I really appreciate it!
 
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chas_m

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Chances are pretty high that you forgot to plug back in (or did so incorrectly) the HD temperature sensor cable on the front. I have done that upgrade hundreds of times (used to work for a Mac repair shop) and that was a crucial step -- and I always knew immediately if I had forgotten to do it!

SMCFanControl -- VERY VERY BAD IDEA if my guess is correct. It's a band-aid at best, and really not recommended as it doesn't fix anything, just makes things worse or burns out the fans much faster.
 
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I know for sure that the cable on the front is plugged in. I have turned on the machine when it is open with and without the cable plugged in, and I know that the HD temperature sensor is doing something since the fan speed will eventually slow to a reasonable 1500-2000 RPM on it's own when idling at the desktop. The fan mainly picks up when booting and using applications.

I'm not sure what to use or do to this mini beyond smcFanControl. I would like replace the sensor cable, but they seem to run for around $20-$25 online, and I consider that too much to pay for something that might not even fix the problem. Do you have any recommendations?
 
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I would just pay to fix the temp sensor also i would check something as well check the memory before you jump into a temp sensor.

The reason i say this if the computer has the wrong type of memory installed you can cause the same fan issue.
 
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Hello everyone,

This morning I opened up my mini and tinkered with the hard drive temperature cable and and fan, and I am now excited to say that the once-troublesome fan is working quite normally. I am honestly not sure how to describe what I did to reach the solution beyond a little bit aimless tinkering, but regardless, I'm ecstatic.

Thanks to everyone on Mac Forums for helping me with this issue! I really appreciate the help and support, and am so happy to have this cute little Mac in a usable state.
 

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