Running a G5 iMac with a disconnected fan?

dodginess

Registered
I've just acquired a G5 iMac today (first time ever that I've been given a good machine, and not something destined for the scrapheap - go me!) and am trying to get to grips with the dreaded fan noise. Maybe it's just me and my sensitive little ears but the noise is completely intolerable and is not something I'm going to get used to any time soon.

Even if it's not recommended, can I run this machine for any length of time without the fan(s) connected or will it just shut down? The reason I ask this is because I used to have exactly the same problem with my eMac and I just whacked a resistor in line with the connector and been happy with the sound of silence ever since - the back of the case gets slightly warm, but nothing compared to what some machines get with their fans running full-tilt.

I should add that I'm not rendering CGI frames for the next Pixar movie or running a particle simulator - cpu usage rarely gets above a sustained 10%-15% on a good day because I just write emails and PHP scripts for a living :rolleyes: Ok, I do a bit more than that but from my eMac's perspective, it's not exactly being pushed...

Thanks in advance for any advice,

Dodg
 

DeltaMac

Tech
I'm surprised as you wouldn't notice the fan, unless the iMac is already operating at a high temp, or perhaps the cooling vents are partly plugged.
I understand how you would feel about an eMac, as that fan always runs at a constant speed, and never varies unless you just turn the eMac off - or put it to sleep, otherwise, the fan drones on...
The iMac G5, on the other hand, has a variable speed fan, which would kick up when needed, otherwise operates at a fairly quiet idle.
There's a couple of things to check (don't even consider disconnecting the fan - the G5 naturally runs much hotter than a G4, and that will definitely be a path to early destruction.)
Make sure the long horizontal vent near the top in back is completely clear. That is the exhaust for the cooling air, and will almost always be warm during use. I then like to use a vacuum brush along the perforated area on the bottom, to suck out any lint/dust etc that might accumulate there.
Which iMac G5 do you have? The processor speed will tell me a lot. There should be a serial number sticker on the bottom of the "foot", or you can check under your Apple menu/About this Computer. The worst one to repair is the newest G5, which has a built-in camera in the top of the front bezel.

Finally (here it is), the most common reason that the fans run at top speed (and they do make a lot of noise when that happens), is that the temp sensor on the hard drive has been disconnected or removed completely. The fans will crank to "noisy", and all you need to do is get that temp sensor connected, and that will bring the fans back to quiet again. The sensor should be mounted on the side of the hard drive, and has a tiny 4-wire black cable that runs to the logic board. So, the hard drive on the G5 has 3 connections. The normal power, and SATA data, and - important for you - the temp sensor.
Do you know how to open up the back? this is assuming that you DON'T have an iSight iMac (with the camera)
 

dodginess

Registered
Thanks for the advice - very helpful for an iMac newbie :) It's interesting you mention the hard drive sensor. Another machine of mine (unmodified) kept randomly locking up and when I checked the system profiler the hard drive was reporting excessive temperatures...when I took it out that thing was certainly cooking on gas!

I think I have the original model (20" screen, 1.8GHz processor, no wireless and definitely no camera). I tried it again today and the noise wasn't too bad, so maybe I *will* get used to it after all. The fans went a bit berserk when I booted into single user mode though - worse than my eMacs in fact. I had a quick look through the manual that came with it and there are instructions on how to open up the case, so I'll see how I get on - thank you for the heads-up before I do this though as I'll know what to look out for. That was another thing about eMacs that I didn't particularly like - I could never get all that screening back in place when I needed to change a drive, plus I always used to forget about that tiny little cable attached to the case.

Thanks again,

Dodg
 
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DeltaMac

Tech
Great!
There's a SMU reset button inside that model iMac G5. Open it up, look for the two reset buttons - near the open fan roughly top center of the logic board. The SMU reset button is furthest from the fan. The other button is actually a power button, which gives you the ability to power on the computer with the back cover off the computer.
With the back off, press and release that SMU reset button. You only need to press that button once.
While that's opened up, take a look at the hard drive, and make sure that the temp sensor is in place, and that third cable is actually attached to the logic board. The sensor is on the side of the hard drive, almost touching the upper end of the memory slots.
You can also look at the various capacitors (all those little silver cans) checking for swelling or leaking, which will predict future problems for your iMac.

Ha! ha! I know what you mean about the tiny cable inside the eMac outer cover. I have been inside literally hundreds of eMacs, and sometimes forgot that connector, or broke it off accidentally (way too easy to do that!)
 

dodginess

Registered
Thanks for the heads-up on that - you sound like a real pro at this kind of thing! :D Looks like I got exactly the right machine, from a maintenance perspective at least. I read that with the iSight model you have to take the screen out? I was always one of those kids that took things apart and had about six screws left over when I put them back together again - although that still seems to happen with me and laptops so I try to not to fix those any more.

I'm going to open the case in the next couple of days to give the internals a quick spruce-up so I'll see what's going on inside and report back. Another thing that's really handy now is having another machine to work from while I've got the other one opened up. Also, I used to work for a company whose imported products got hit by "capacitor bulge" syndrome so I'll keep this in mind as well - I was able to source a replacement capacitor for them in the end but some of the other internal components didn't work so great afterwards...

Anyway, I really appreciate your help with this, so thank you.

Dodg
 

DeltaMac

Tech
Ah - then you'll like to open the back of your iMac. You just loosen the screws on the back cover - they don't need to be removed
 

dodginess

Registered
Ok, that sounds good...I think even *I* could manage that one. Then again, we're talking about the same person that nearly stuck a soldering iron straight in their eye - I went to rub my eyes as the fumes had gotten to me and forgot what I was holding in my hand... I've done the same thing with a scalpel too :eek:

Thanks,

Dodg
 

DeltaMac

Tech
I was in a soldering class some years ago, and caught a motion on the edge of my vision. Looked to my left just in time to see one of the other students, testing the soldering pencil to see if it was hot enough. Yes, you guessed it! He quickly stuck out his tongue, and ... and... (still hurts when I tell the story - no, it was not me! :D )
Scalpel, eh? remind me to always stand behind you.... :D I'll let you go first!
I was at a hot chili pepper eating contest, watching the spectacle, saw one poor sod eat a couple of extra-hot peppers, which he held in bare fingers, then started to get tears in his eyes, and proceeded to rub his eyes, with the same fingers.... ! NOT fun to watch. (maybe a little fun! - glad it wasn't me)
Hey, good luck, let us know what you find out...
 

MacOSX1058

Registered
I was in a soldering class some years ago, and caught a motion on the edge of my vision. Looked to my left just in time to see one of the other students, testing the soldering pencil to see if it was hot enough. Yes, you guessed it! He quickly stuck out his tongue, and ... and... (still hurts when I tell the story - no, it was not me! :D )
Scalpel, eh? remind me to always stand behind you.... :D I'll let you go first!
I was at a hot chili pepper eating contest, watching the spectacle, saw one poor sod eat a couple of extra-hot peppers, which he held in bare fingers, then started to get tears in his eyes, and proceeded to rub his eyes, with the same fingers.... ! NOT fun to watch. (maybe a little fun! - glad it wasn't me)
Hey, good luck, let us know what you find out...
LOL i always love your stories that was a good one :D Anyways on topic with post i do not know much about a iMac G5 infact i know NOTHING at all about them but i know about computers in general and it is NEVER a good idea to disconnect a fan. There is a program to control fan speeds but as far as its name and ability to work on PPC Mac is beyond me.
 

ElDiabloConCaca

U.S.D.A. Prime
I don't want this to devolve into an off-topic discussion of Darwin Awards, but I had to chime in about my friend, Matt.

Matt's eyes were dry, and he wanted to put a drop of Visine in them. So he reached for the bottle of Visine sitting next to his bed, leaned back, and put two drops in each eye.

Something was terribly wrong, though, as the cool, refreshing, wet sensation he was expecting was, instead, a horrible burning sensation.

Instead of grabbing a Visine bottle, he had accidentally grabbed a bottle of Sweet Breath.

After a trip to the emergency room to get all cleaned up, he told me that for the next two weeks, he now knew what it felt like to have "minty-fresh eyes."
 

dodginess

Registered
After a trip to the emergency room to get all cleaned up, he told me that for the next two weeks, he now knew what it felt like to have "minty-fresh eyes."
C'mon, who wouldn't want "minty-fresh" eyes? :D

While we're tangentially displacing ourselves away from the original topic, I descaled my kettle once using a proprietary cleaner (containing a highly corrosive concentration of formic acid) and then got distracted by the dog barking outside. When I got back into the kitchen, I said to myself "hey, it must be time for coffee!" The cup was about two inches from my lips before I remembered what it was I was doing with the kettle beforehand...and yet somehow I can drive a car into town without killing anyone, write computer programs and remember to feed myself :p

Dodg
 

DeltaMac

Tech
Are you required to call the local police before driving in to town, so they know you are on the road? It's only a matter of time until the odds turn against you.... :D
 

dodginess

Registered
Doesn't everyone have police out riders when they go to pick up a few groceries? That must mean I'm *extra* special then :D

Either that or they substituted my car for the Knight Industries Two Thousand a few years back - either way, I'm still cool :cool:

Dodg
 
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