Mm 1,1-6,2 Mac mini 2009 fan spinning at full-throttle after replacing the HDD

[aurora72]

Hello,

I've replaced the harddisk of the Mac mini late 2009 with an SSD. After the replacement, the fan started to spin at full-throttle.

Here's a 1 minute video depicting the problem. The problem is caused by the temperature sensor going defect (the small transistor glued to harddisk) I've put that sensor at the bottom for visibility:

I might have applied too much force on the sensor as I was removing it from the side and that might have broken it down. It has a 3-legged part (transistor?) with the code CG2 written on it. I did a search with the code CG2 nothing related came up. Could it be replaced with a compatible part? Someone suggested short-cutting the temp sensor as a workaround in this 2011 post and I've tried short-cutting the sensor but it didn't change a thing. How to solve (or work around) this problem?

 

[ToniCH]

Why don't you just install the Mac Fans Control and set fan speeds from it? Then you don't have to worry about the sensors. Try it and report back.

 

[DCBassman]

Another vote for Macs Fans Control.

 

[aurora72]

Why don't you just install the Mac Fans Control and set fan speeds from it? Then you don't have to worry about the sensors. Try it and report back.

Thank you for the comment. That app indeed works around the problem but suppose I set it to 1500 (normal) rpm, what happens if the CPU is so overloaded that the fan speed needs to spin higher, say 2300 rpm, does that app block such higher rpms?

 

[ToniCH]

If you set it to static 1500rpm speed then its 1500rpm, no more no less. But if you set it based on sensor then it will increase rpm when needed and you can adjust fan behavior. Experiment to find good settings.

 

[aurora72]

If you set it to static 1500rpm speed then its 1500rpm, no more no less. But if you set it based on sensor then it will increase rpm when needed and you can adjust fan behavior. Experiment to find good settings.

I've set it to 1500rpm then opened a 1080p Youtube video to see if the fan speed would increase. It didn't. It must have increased to say 2000rpm or higher to exhaust the redundant heat.

But nevertheless I've fixed the problem! In this forum post, someone was talking about how s/he fixed the problem by replacing the sensor with a transistor with the code 2N3904 He described which leads of the transistor would be connected to which ends of the twisted pair sensor cable. So I've bought a 2N3904 in a local store for about $0.3, de-soldered the cable from the defective sensor and soldered it to the 2N3904. In the pictures, the cable painted in white (I've painted it to distinguish it between the 2 cables) is soldered to B and C leads of the 2N3904, the other cable soldered to the A lead.

The socket end of the cable where the cable painted in white can be seen as located (towards the inside)

I've just taped the transistor's flat side onto the bottom of the SSD

The talk where the 2N3904 transistor is being used as heat sensor in 2009 Macs can be seen here too

 

[ToniCH]

I've set it to 1500rpm then opened a 1080p Youtube video to see if the fan speed would increase. It didn't. It must have increased to say 2000rpm or higher to exhaust the redundant heat.

Yeah, like I wrote you need to choose "based on sensor" and then it will increase, when needed.

 

[mikezang]

I have a mac mni (Late 2009) and there is El Capitan 10.11.6, then I installed Monterey 12.7.1 to external SSD by OCLP 1.3.0.
Next I am going to extend 4GB memory to 8GB, I want to know if I also need to change my internall HDD to SSD? Please give your suggestion.

 

[ToniCH]

I want to know if I also need to change my internall HDD to SSD? Please give your suggestion.

Its not a must but it would make the machine feel quicker if you decide to install your OS and stuff to internal drive. The internal SATA bus is 3Gbps which is about 6+ times faster than the USB2.0. Even if your SSD could only negotiate 1.5Gbps link speed the bus speed would be 3x faster than the USB. So, potentially very much faster transfer speeds are available.

With the planned RAM upgrade I think you would really feel the difference.

 

[mikezang]

Its not a must but it would make the machine feel quicker if you decide to install your OS and stuff to internal drive. The internal SATA bus is 3Gbps which is about 6+ times faster than the USB2.0. Even if your SSD could only negotiate 1.5Gbps link speed the bus speed would be 3x faster than the USB. So, potentially very much faster transfer speeds are available.

With the planned RAM upgrade I think you would really feel the difference.

Thanks for your suggestion! Though I checked a lot of videos, I am still afraid it is too diffcult for replacing memory and HDD, do you think so?

 

[ToniCH]

Thanks for your suggestion! Though I checked a lot of videos, I am still afraid it is too diffcult for replacing memory and HDD, do you think so?

No, just did it couple of months ago to my 2009 Server. But, I have done many Mac-projects in last few years and things tend to get easier and less intimidating with experience. Just work carefully and slowly following instructions. Don't force anything, if something doesn't come off easily, investigate if you are doing something wrong or if you missed a connector, screw or something. No crowbars are needed with these but delicate touch and thinking before acting.

 

[mikezang]

No, just did it couple of months ago to my 2009 Server. But, I have done many Mac-projects in last few years and things tend to get easier and less intimidating with experience. Just work carefully and slowly following instructions. Don't force anything, if something doesn't come off easily, investigate if you are doing something wrong or if you missed a connector, screw or something. No crowbars are needed with these but delicate touch and thinking before acting.

About the size of HDD/SSD, is it 2.5" or 3.5"?

 

[mikezang]

By the way, I want to replace optical drive with SSD and let this SSD as boot driver, is it possible?

 

[ToniCH]

About the size of HDD/SSD, is it 2.5" or 3.5"?

You need a 2.5" SATA SSD. No big 3.5" drives in Minis. And I don't think they even make 3.5" SSDs or at least I've never seen one. Don't go anything fancy on the SSD, the bus is old and not 100% of SSD's work in it. You need one that is directly or backwards compatible with SATA-II. There are many threads discussing this on the forum.

I personally have lots of different older SSDs that work with old machines, lately I have been buying mostly Intels PRO-series 2nd hand. Cheap and last a long time.

By the way, I want to replace optical drive with SSD and let this SSD as boot driver, is it possible?

Might be but why complicate things? Just replace the hard drive with a SSD and that is it. You need to remove the drive caddy incl. the SuperDrive optical anyway to upgrade the RAM.

 

[mikezang]

You need a 2.5" SATA SSD. No big 3.5" drives in Minis. And I don't think they even make 3.5" SSDs or at least I've never seen one. Don't go anything fancy on the SSD, the bus is old and not 100% of SSD's work in it. You need one that is directly or backwards compatible with SATA-II. There are many threads discussing this on the forum.

I personally have lots of different older SSDs that work with old machines, lately I have been buying mostly Intels PRO-series 2nd hand. Cheap and last a long time.

Might be but why complicate things? Just replace the hard drive with a SSD and that is it. You need to remove the drive caddy incl. the SuperDrive optical anyway to upgrade the RAM.

The firmware version is MM31.00AD.B00, does this support 8GB memory? how can I upgrade it if it deosn't?

 

[Nguyen Duc Hieu]

By the way, I want to replace optical drive with SSD and let this SSD as boot driver, is it possible?

Check the connector. If it is SATA, then yes, if it is IDE, then no.
RAM can be increased to 8GB.

 

[ToniCH]

Check the connector. If it is SATA, then yes, if it is IDE, then no.

Couple of different SuperDrives (Sony, Pioneer) in 2009 Minis, but both are SATA IMHO. But, I still cannot see the point.

Ps. I don't think there is firmware updates to late 2009 Minis, only early 2009 and 2010 minis (?).

 

[Nguyen Duc Hieu]

Couple of different SuperDrives (Sony, Pioneer) in 2009 Minis, but both are SATA IMHO. But, I still cannot see the point.

Ps. I don't think there is firmware updates to late 2009 Minis, only early 2009 and 2010 minis (?).

A caddy bay is needed to install 2.5" SSD to the place of the old ODD drive.

 

[mikezang]

A caddy bay is needed to install 2.5" SSD to the place of the old ODD drive.

Which height do I need, 12.7mm or 9.5mm?

 

[Nguyen Duc Hieu]

Which height do I need, 12.7mm or 9.5mm?

Normally you will need a 12.7mm. ODDs of that era were quite thick.
9.5mm may also do, but may not be very tightly fit.

 

[aurora72]

Thanks for your suggestion! Though I checked a lot of videos, I am still afraid it is too diffcult for replacing memory and HDD, do you think so?

I suggest that you use a pair of putty knife / scrapers to open the case. It's also suggested that you polish the edges of the knife with a rasp and then apply some oil for smooth penetration between the plastic base and the aluminum case. Here is a pair of putty knives in action: