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[tbova72]

I am in need of some advise/help. I have a Powermac G4 1.25ghz MDD with 9.22 and 10.4 installed on an SSD. When booting into OS 9 the case fans run; however, when I boot into OS X, the case fans start at full speed and then shut off once the system is booted. If I boot into safe mode, the case fans stay on and seem fine. I have reset PRAM, done the SMC reset several times, removed and reinstalled hardware components, etc, etc... It wouldn't seem to be a hardware issue, since the fans are running in safe mode, as well as OS9, but at this point, I am just baffled by the issue. I suppose it could be the PSU, but why does it work in safe mode and OS9?  Just applied new thermal paste, with the same results.  It seems like as soon as OS X is loaded, the fans gradually lose power, then cut off entirely.  If anyone has some advise or suggestions on what I might try going forward, it would be greatly appreciated.

[FdB]

Are all fans shutting off completely when you boot into OS X... or just ramping down (but still working slower) after full boot? I'd try a fresh, clean install of OS X.

[coachla]

This topic keeps rearing it's head. Here's  the solution to all this hoop-jumping. It will also eliminate RF interference in the MDD audio which is horrendous. OSX runs hotter than OS9 on the MDD. My 1.25 dual MDD has been running like this since I bought it new back in the day:

Disconnect the fan lead from the mobo controller. The little fan by the mobo is useless. Take the two leads from the big CPU fan and connect them to a drive molex connector on the PSU. You have three options. 12 volts, 7 volts or 5 volts. You want to use the 7 volt option. Connect one fan lead to the 12 volt on the molex and the other fan lead to the 5 volt on the molex. This gives you the difference which is 7 volts. Obviously you want the fan to blow in the direction of the CPU. Reverse the wiring accordingly if need be. You need only this fan to cool your MDD. 12 volts is too loud. 5 volts is not enough speed. 7 volts is perfect. This will give a continuous  quiet fan speed and extremely good temperatures.

[tbova72]

That sounds like the solution I will have to go with, because nothing else is making sense.

Thank you.

[FdB]

Might also note that coachla states that...
"I run all my machines bare board.  Throw away the case.
Just set a fan directly on the heatsink. Your cpu will run cold.
It's a waste of time fussing with cases".

[tbova72]

Yeah, I could see that.  I will mainly be using this machine for OS9 anyway; it was just driving me crazy that it worked in one OS and not another. 

[coachla]

Here are three MDDs with fans running on 7 volts. Usually there were three duals, a 1.25 and two 867s overclocked to 1ghz. But here I had (on the backside with a Stealthport) a Firewire 800 1.25 running Tiger. I'm also posting these on their own topic, because there are so many discussions about this.

[tbova72]

Thanks.  Do you have a suggestion on where to purchase the molex to fan connector cables?  I see a couple on amazon for 2 pin, but some people are saying they are cheap.


Thank you.

[coachla]

Since it is a female connector coming off the PSU I just stripped and inserted the bare wire into the connector. Then I taped over it. If you strip and fold back the wire over the insulation it will be thick enough in diameter as a male pin would be. Shrink or tape over it. I would choose Ebay first for such connectors.Whatever gets the job done.

[tbova72]

Right on, thanks for the tips.