I have a beige G3 Desktop. Stock CPU was a 266MHz G3. I found a G4 400-500MHz zif in a Blue & White G3 that would not boot (Free Geek project purchase). I was able to get the G4 to 533MHz and it is stable. It does get quite warm, so I thought it would be best to add some active cooling. I have lots of Apple fans salvaged from old dead macs over the years. My selection was the rear intake fan (above the power plug) from a 2009-2011 style iMac. The pinout is always odd on the Apple fans, but Google AI gave me this:
Since the G3 has no temp sensor and no PWM controller, the easiest thing is to run the fan full speed by joining the PWM to the VCC line. This is a 12v fan. To keep the noise down, I went with the 5V line instead of the 12V side of the molex connector. I 3D printed a simple adapter to hold the fan in place. It was not perfect so I added some bodge wire to hold it in place. I was going to use hot glue, but if temps rise, that would not hold.
Yes, I will eventually solder the wires and shrink wrap them, but for the test, it worked fine. After 30 minutes of run time, the CPU heatsink is only slightly warm to the touch (instead of untouchable).
Since the G3 has no temp sensor and no PWM controller, the easiest thing is to run the fan full speed by joining the PWM to the VCC line. This is a 12v fan. To keep the noise down, I went with the 5V line instead of the 12V side of the molex connector. I 3D printed a simple adapter to hold the fan in place. It was not perfect so I added some bodge wire to hold it in place. I was going to use hot glue, but if temps rise, that would not hold.
Yes, I will eventually solder the wires and shrink wrap them, but for the test, it worked fine. After 30 minutes of run time, the CPU heatsink is only slightly warm to the touch (instead of untouchable).