People do not notice when the fan dies.
When they notice the fried electronics it is too late.
For this reason and for generally prolonging the life of the hardware I prefer fans run at full speed.
I have made photos from my work inside the cramped power supply.
But I am not sure whether it is desirable to post photos.
The work with high voltages is not recommended for unskilled people, which should not be encouraged to do such things.
If you are skilled, you won't need instructions how to connect the fan to 12V anyway.
I did that and noticed that the fan is quite weak for my taste.
It is better than before, when it an airflow was noticeable only barely.
I do not understand.
for the cooling me I multiply the fan and I connect them in 5v or place of the 12v as these possible. for decreased noise.
there is also the laptop fan with the heatsink aluminum and copper, but we must choose the model that will go well with the macintosh
What I mean is this typical situation:
PC with temperature controlled fan. Fan getting old or defective. Turns slower and slower, finally stopping.
User does notice nothing. Only thinks "that is a nice quiet computer!"
PC without cooling runs until overheated electronics finally break down.
Remove all the electrolytic capacitors and replace them with tantalum capacitors. Reason, electrolytic caps will eventually leak and cause damage to the board itself.
If applicable for the machine you are considering to work on, remove the old thermal paste and add fresh thermal paste.
Rather important: remove any old batteries on desktop machines and replace it with a fresh new battery
These three points will certainly keep your mac in good working condition for years to come and avoid overheating and avoid boards that are beyond repair.
As an example, 10 years ago or more I gave a friend of mine an iMac G3 333MHz, she called about 3 years ago noting a problem. It wouldn't switch on but there was some life in it. A year or two later she asked me if I wanted the machine, I said yes, I took it home and found that the internal battery had leaked all over the main logic board. It was literally beyond repair so I purchased a new logic board on eBay for about 30 bucks, gave the new board a fresh battery and wiped it clean with Isopropyl alcohol. As I had opened the machine up partially I went all the way and cleaned it all up inside. Along the way I discovered that the battery's end of life might have ended in some type of small explosion such that the battery's innards had shot up and made contact with a metal chassis that left a stain that couldn't be sanded off completely. For the chassis I had to sand off what I could and then went about sanding the entire chassis and then gave it a fresh look with several coats of silver spray paint. The plastics were all buffed and the end result is truly glorious. The machine's plastics look just beautiful and because the insides are so dust free the end results are spectacular. The project took several days to complete but the results are worth it.