There is a fan on the chassis of the G4 Powermac opposite the motherboard which seems like it is there to blow air onto the CPU and motherboard. See attached picture.



Anyway, the times i had the case open i have never seen this fan working. The most it does is looks like it is trying to start when the mac is switched on. I never saw or heard it actually working.

I didnt really bother as i mostly use MorphOS and never really had any problems except once MorphOS froze after long use.

But yesterday i left the mac on all day, though most of it was "sleeping" as i was out.

But after using it for about 45mins-1hr it froze.

I rebooted and it was getting stuck while booting OSX and MorphOS had corrupted graphics.

I restarted again and OSx booted up fine but after 2 minutes using Safari it froze and gave me an error message saying to Hold the power button down for 5 seconds or else reset.

I reset and it started up fine, but after a few minutes browsing i got the same problem.

Question time:

Is that fan meant to be on all the time?
Is it normal that i never saw it running?
Is this an overheating sign?

Also, i should note that the last time i had this problem was about 3 weeks ago because of a faulty ram chip which i changed.

Yesterday i DID open the mac (before the problems started) and tried some spare ram i had. But the spare ram was broken and i simply replaced back to the ram i had (where it was fine).

The ram simms were 256/128/256 and i inserted them as 256/256/128.

Should i put them as 256/128/256 again?

But the fan... thats worrying me, maybe.

MAC-PC-HD-Fan.jpg

[ Edited by Dougal on 2010/11/4 12:25 ]

OK, could be ram. Dont think its overheating as it froze after being on for less than 3 minutes and i checked the the heatsink was still cold.

I tried re-seating the ram and so far it seems ok.

The fan should work all the time.

With my overclocked 1Ghz to 1.2 Ghz I noticed some graphic garbage also. Strange thing the garbage was still there after a cold start and disappeared while changing from 16bit to 24bit colors and back. So not sure it was because of the overclocked cpu.

Is that fan meant to be on all the time?

Yes. It is always on in my GBE Power Mac.

Is it normal that i never saw it running?

Of course it is not normal.

As for memory sticks. I have 512/512/128 set and they work in any order (even leaving slot 1 empty). I've had one faulty 512 stick however. It has been not seen when used with another, working one, and the Mac refused to boot, when trying the stick alone.

All the G4 Powermacs are prone to overheating (except MDD) especially when used with 3rd. party cpu modules. There's even no exhaust fan on models predating Digital Audio (don't know for sure about GigE). The 120mm fan blowing to the motherboard is temperature controlled, but it should still be on all the time. If it's overheating, I'd recommend replacing the PSU fan, with more powerful one. Or if your model has the exhaust fan, then replace that instead. Without the shroud, it should be possible to use 70mm fan instead.

I swapped the cpufan in my Quiksilver with a faster one from a PentiumIV heatsink... the original is a really slow fan that doesn't move much air. That and some new thermal paste between cpu and heatsink.

Oops, made a mistake, the 120mm fan is actually blowing out by default (atleast on Quicksilver). I have turned it around on my Mac and replaced the cpu & psu fans with more powerful ones.

Maybe the fan does not work when the case is open?

it should run... always.