iMac G5 fan problem - please advise

I was hoping someone who knows Macs might be able to help. I've UTFG (used the fucking google) but there is a hopelessly large amount of unfocussed information that it was very tricky to sift through effectively.

I have an iMac G5 (iSight), the last 20" model before they switched to Intel. It's worked reliably since I bought it a few years go until about two months ago when it just broke down. The main logic board was kaput. Luckily I was able to have it repaired free of charge by Apple on the very end of my extended Applecare warranty thing.

I've had it back now or a few weeks and it's working really well... except that the fan comes on and runs fast and loudly periodically. For the most part it runs as quietly as it should, but if I open a large CAD drawing (for instance) the fan gradually ramps up to full speed. When I close the file it gradually winds down and returns to normal.

In other words, when the computer is working harder the fan seems to run faster and louder. Can anyone shed any light on this for me? It really is intolerably noisy and 95% of my work is in using such drawing files.

Many thanks in advance for any guidance.

Higher CPU usage causes more heat which causes the fan to spin up to compensate. Sounds normal to me.

I know for the Crapintosh laptops you can get some software that controls the fan speed manually.

Crapple in their infinite wisdom turn down the fans to have a quieter machine. The guys at work with crapples have some 3rd party app that allows them to increase fan speed to stop their machines over-heating.

I'll ask one of them what it's called..

Also, check that the fan is clean and nothing is obscuring any of your computer vents - the cooler you can run your machine the less the fans will be needed. I know my laptop sounds like it's working harder when I let dust build up in the fan vent area.

smcFanController is the application they use to control their mac laptop fan speed.

Any more edits Hippy? :)

Yes. "smcFanController is the application they use to control their mac laptop fan speed."

You'll never get your post count up like that.

It's all pristine after having been serviced recently. I know fans run faster to cope with high CPU usage but I've never known them to run this loudly. It's exceedingly distracting. The drawing files themselves aren't that big either, miniscule in fact compared to some that I have made in the past with no bother at all. It's a desktop iMac rather than a laptop BTW.

I'm not concerned with post counts (except when people encourage me to ramp it up near milestones).

I like to help, even Mac users need some love.

It's all pristine after having been serviced recently. I know fans run faster to cope with high CPU usage but I've never known them to run this loudly. It's exceedingly distracting. The drawing files themselves aren't that big either, miniscule in fact compared to some that I have made in the past with no bother at all. It's a desktop iMac rather than a laptop BTW.

How do you 'service' a mac?

Is it cpu fan or a case fan or another fan making the noise?

I know it's a desktop. I'm just saying you might be able to use the controller on your machine. At least find something to show you your cpu and case temps so you have an idea if the fan IS actually necessary for what you are doing.

Or, just buy a PC.

I should say that I'm particularly looking to compare Macs and PCs, though thanks for the otherwise helpful input. When I said serviced, I meant that it had been cleaned up, repaired and put back together by the smiley homogenous people at the Apple 'store'.

I'd have a google for temperature sensor software suitable for your machine and keep and eye on temps, fan speed and cpu usage to see if it looks right or wrong or if there's a pattern.

They may have also bump the fan or installed a louder fan or done any number of things to a fan in the machine during servicing which has made it louder. Maybe they removed some insulation.. or took out the dead rat that was blocking the vent or..

I'll look into that, thanks Hippy.

Have you installed all software updates for your machine? Those machines were known to be quite loud unfortunately...

SMC is one option, as is making sure that nothing is obscuring the vents at the bottom of the machine and that it's in a fairly cool/ventilated area. Be aware that manually adjusting temperature control can cause problems, although the default ranges that OS X uses are very "safe".

Also make sure that the vent grill (bottom edge of the screen) is free from dust, etc. I would say to open it up and have a clean out of dust, but there's no point if it's been to the Apple store recently.

Finally try resetting the SMU, it's possible that the power control settings are slightly out after having the LB replaced.

Download X Resource Graph and see if any of the steps above help whilst trying to re-create your problem.

It's possible, but unlikely, that you have bad RAM installed, this stops the OS getting correct information from the hardware of your machine which signals an "emergency" ramping of the fans. (Check for this by running Apple Hardware Test from your install disk).

You may find that using a different version of OS X (Leopard/Snow Leopard) will also help as they have a better process for temperature management across all machines... a long shot though as your hardware problem may be unique.

Oh and don't buy a PC, heh.

usually fan speeds are controlled by your cpu temperature, sounds like maybe when they installed your processor into the new logic board, they didn't apply the thermal paste well or clamp the heatsink sufficiently. basically, the idea is to place a thin layer of thermal compound (goop that transmits heat well) between the processor and the heatsink to transfer the processor heat to the heatsink which is effective at dissipating heat since it has lots of surface area. the same thing can also happen on your gpu (graphics chip).

there are some pics here: [ame="http://forums.macrumors.com/showthread.php?t=677120"]Pictures of re-applying thermal - Mac Forums[/ame]
if you are comfortable doing it yourself, otherwise anyone who has built a pc should be knowledgeable in applying thermal paste. arctic silver 5 is generally considered the standard high performance thermal compound.

p.s. how do you open CAD drawings on a mac? ;)

What JonoMarshall said.

In addition, on my wife's old iMac (G5, pre-iSight edition), the fan started to squeak intermittently. Very high pitched and irritating. I found a thing on the internet, that showed an iMac in various states of disassembly (in photographs), pinpointed the main fans, and put a single drop of oil (it was sewing machine type oil - actually from my hair clippers) on the spindle of the fan. No more squeaking.

But you definitely need to try resetting the power management settings via that hold-the-power-button-down-till-it-beeps thing.

Vectorworks, not AutoCAD.

They wouldn't have replaced the processor, they would have replaced the whole LB. (The problem with iMacs was that the LB transistors couldn't take the ongoing current and eventually bulbed causing display anomalies and eventually failure.)

No need to worry about the paste, it will be a problem with the fans on the LB (as the LB would've been refurbed and potentially won't be an exact match to the original), or with an outdated OS, or a localised problem (environment, dust, etc).

Also, as a side note, check that it's not just one app causing the problem as it could be down to bad code (stopping the OS from communicating efficiently, resulting in the "emergency" fan speed) or ongoing (bad/unnecessary) memory requests, causing a memory hog/processing loop.

How do you bring up a current process list on a mac?

It does seem to be just Vectorworks actually. Thanks for all this help guys, it's very helpful and generous of you.

I run SMC fanc controller on my Macbook Pro. It doesn't look like it supports iMacs yet, though the author says he may add it in later. Whether that means the software won't run at all, or the temperature and fan speed readings are out of whack, I don't know.

Downloadable from here:

http://www.eidac.de/

How do you bring up a current process list on a mac?

There's a utility that ships with the OS called Activity Monitor. You just run that. Or get a terminal and ps aux.

I've just opened a shitload of applications (not including vectorworks) at once and the fan is behaving normally. It seems to be entirely to do with when I open Vectorworks.

They wouldn't have replaced the processor, they would have replaced the whole LB. (The problem with iMacs was that the LB transistors couldn't take the ongoing current and eventually bulbed causing display anomalies and eventually failure.)

No need to worry about the paste, it will be a problem with the fans on the LB (as the LB would've been refurbed and potentially won't be an exact match to the original), or with an outdated OS, or a localised problem (environment, dust, etc).

pretty sure the imac g5 heatsink doesn't have a fan attached. i just meant when they transferred the processor to the new logic board they may not have seated the heatsink proper with compound. would explain higher temperatures triggering a high fan speed on cpu-intensive tasks like loading vectorworks. do you have the same fan noise when playing a 3d game for example?

an SMU reset also can clear up problems like fan speed control. you just need to unplug everything for 30 seconds, and press the smu reset switch at the rear (tiny pin hole button), plug in, boot up

and that doesn't affect or format owt?

I've just opened a shitload of applications (not including vectorworks) at once and the fan is behaving normally. It seems to be entirely to do with when I open Vectorworks.

opening many apps doesn't necessarily stress your cpu, just uses up ram. 3d games, SETI@home, folding@home or xbench http://www.xbench.com/ would be a better indicator of whether the issue is vectorworks related