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iMac G5 Cooling Fan Mod/Reports on Temperatures
Posted: 7/26/2005
Last Updated: 10/19/2005 (More iMac G5 owner reports)

I've not watched Apple's forums for 2GHz iMac G5 threads to see if anyone else reported that model overheating in use, but yesterday a reader sent a mail saying his was and mentioned adding a cooling fan. (See the other reports section below for other iMac G5 feedback on this.)

"iMac G5 overheating fix!
I was liking my new iMac G5 17" computer, but after 30-40 minutes in 78°F ambient the thing would freak out and lock up; too much heat in too little cabinet space. I tapped into the existing ducting just under the plastic and mounted a 120mm fan good for 50 cfm at 16 volts powered by an external adapter; this is giving CPU temps about 25°F lower than before, and 12-15°F lower on the hard drive. We may offer this to users here if there is sufficient demand. I hope to gain approval by Apple so as not to void any warranties.
Those with overheating concerns should download the Bresink Temp Monitor for on-screen readout, and consider our mod if CPU runs above 170°F much. This mod should be doable on the 20" iMac G5 also.

(I asked what the CPU speed was as I didn't remember anyone else reporting any overheating problems-Mike)

It is a newish machine, 2.0GHz CPU, and it overheats in 30-40 minutes here in a 78°F office, very frustrated until I added the fan. Using the Bresink Temp Monitor we were seeing 175°F on the CPU (see http://www.bresink.com/osx/TemperatureMonitor.html, a free/trimmed down version of HardwareMonitor.html. As far as I know it's reading an adjacent temp sensor, not the actual internal CPU junction temperare as the G5 CPU chip is rated for higher temperatures than that-Mike) just before the thing locked up, now seeing 130-150°F most of the time.
Tim at E-Tech Systems Phoenix"

If I had an iMac G5 that I thought was overheating, I'd contact Apple as the stock system as-is shouldn't be overheating. (And I doubt most iMac G5 owners would want a fan added, but that's just my opinion. However the first reader reply asked if Tim checked to see if the internal fan was working before adding this "ugly" mod.)
I welcome other iMac G5 owner comments on system temperatures and if they've seen any overheating problems. I asked Tim about the stock internal fan (was it working) and mentioned the first reply to his post called it a butt ugly hack basically - although being on the back side it's not seen in use. (What I wanted to know was if anyone else had any overheating problems with an iMac G5, which would surprise me unless there was something wrong with the internal fan/fan control - however see the later update below from a 1.8GHz iMac G5 user that noted overheating problems in Final Cut Pro use even with a 20-21C ambient temperature.)

" Ouch! I was half expecting a request for white fans....... There is no room to do another fan internally; (I asked again - my question was if the stock internal fan was working-Mike) my fan does port to the ducting in between the plastic and a metal liner so it is done in a studied manner. Customer units (and my own) will get made with tidier wiring.

As to my unit. the Apple Biltmore guys had the machine for two days and, of course, in a 73°F room it did not lock up; my office is more like 79°F. A factory guy told me it should function in temps as high as 90°F, so my mod is needed here for me, and it is hard to predict who else is having problems. I have an e.mail here from a chap in Venezuela who works in 80°F and he may be our first taker... he writes:

    " Tim, thanks for the e-mail, I Live in Venezuela my Imacs are overheating all time temp here +- 80 f
    Thank you, Hermes"

Heat kills electronics, even over time, so why risk a $1200 midplane over what I feel is a marginal thermal management design?

(I asked again if the stock internal fan was working-Mike)
I am pretty sure they were working; the Apple Store tech found no problem, Hardware Test ran okay even here, I noticed that Hardware Test ran the fans hard (?) unlike normal use.
(When booted from the Test CD, the OS's fan control software isn't running so the fans default to a fail-safe mode. Same is seen on the G5 Towers-Mike)

Look at an iMac G5 closely; all air intake appears to be the perfs along the bottom of the case, all venting out is the slit at top rear which is a mere five square inches; these things draw near 180 watts and the temps I was seeing just suggests a marginal design in the name of Sleekness...

(he later added)
I have addressed one problem and solved two problems here; I now have a machine that will run all day instead of 40 minutes, and and unexpected benefit is that the fan noise now is one continuous pitch, not chopping up and down, which previously very annoying. They can void my warranty if they want to, at least I have minimized the likelihood of chronic heat damage......

I do not expect everyone to need or want this mod, those in warmer climes and units approaching end of warranty will be among the first.
Cheers, Tim"

I don't own an iMac G5, but I've measured some very high internal temperatures in the past in even a stock G4/450 Cube (using a thermocouple and meter). I added an 80mm fan in the bottom of my heavily modified Cube (see past articles on the systems page, Cube section and the CPU upgrades page, reviews of Cube upgrades) which lowered temps dramatically (which helps with drive longevity too).
Below are some photos Tim sent of the tacked-on cooling fan:

Cooling fan pix

screenshot of reported temperatures

Other iMac G5 Owner Reports on Temperatures (Most recent first)
(I welcome other iMac G5 owner comments on system temperatures and if they've seen any overheating problems.
NOTE: Setting Energy Saver's Performance Option to "Automatic" can help lower temperatures (by lowering CPU speed during idle/light loads).

(added 10/19/2005)
" just got brand new imac G5 2.0, 20" yesterday (18th). My serial # is not included in the apple/imac repair numbers posted at apple. This morning after i logged out and left the imac on for a little while -- maybe 10-15 minutes at most, i came back in my office and smelled the acrid/burning plastic/ozone smell. so i immediately turned it off.
rebooted okay a few hours later.
noticed that it did not seem to go into power saver mode while sitting at the login window. (I'd log-in, to make sure the OS was running normally and not just waiting for a login to start all processes/tasks.-Mike) i left it on all nite logged in, energy saver working, and no smells. so am now sitting waiting more than 40 minutes for someone named Prem on the new apple chat/chat with apple agent window ....http://chat.info.apple.com/ .... sigh..... so far this is not a good sign....
anyway, I keep reading the temp/heating probs are not just limited to early revisions and the date on my imac box is 8/29/05, so i guess that  this seems to confirm that.
best regards, thnx for your site

I don't know if this is a random problem or not but even some later builds (that shouldn't have the capacitor problem) have noted high internal/drive temperatures.
This makes me wonder about the new (Oct. 2005) iMac G5s which are slimmer and have faster CPUs (not sure if they're lower voltage CPUs than the previous 970FX CPUs).
If any reader gets one of the new 2.1GHz iMac G5s and runs Hardware Monitor or Temperature Monitor (assuming they support the new model), let me know what temperatures are reported (including HD temperature) in heavy/extended use.

(added 9/23/2005)
" i purchased a 20" 1.8 GHZ G5 iMac in April, 2005 and have had absolutely no problems with it (fan or otherwise).
is it possible that this is another example of the problem seeming bigger than it actually is because people are more likely to be vocal if they have issues?
(It's always true you're 10x more likely to hear problem reports (on anything), and some here didn't have functional problems (shutdowns, etc. from overheating) but were just concerned about the reported temperatures. Of course the capacitor issue with the early iMac G5s did affect a large number of systems (many more than will ever be reported in one place) but later systems should not have that problem.-Mike)

i, of course, feel great sympanthy for those experiencing the issues, and hope that Apple resolves the problems.

He didn't mention any temperatures so I assume he never installed temperature monitor (or other 3rd party reporting utils). Just curious if he saw temps as high as some reported here. (BTW - the Energy Saver's Performance option set to "Automatic" can often result in lower temperatures in typical/casual use, when the system isn't heavily taxed.)

(added 9/22/2005)
" I have iMac G5 1.8GHz 20 inch that frequently reaches temperatures above 170F (my max recorded is 177F) while playing RPG games. It hasn't locked up or shut off to this date. I have asked our local Apple retailer and Apple Support and Product Specialists what the safe operating temperature should be, but no one at Apple will give me an answer and the retailer says that that information is not on any spec sheet.

I had loud fans to begin with and had the mid-plane re & re done. Got a another bum one, and had it replaced by my original retailer. The fan is now not very loud but the pitch is very annoying(I wear earphones when the fan kicks in).

My wife's iBook G4 is running at 154F to 158F when she plays RPG games (Pensioners need something to do). When at the max temperature, the disk will not eject nor will a disk image unmount. Had more trouble with this machine then we have had with almost 20 years of Mac ownership.

So far, Apple's answer to both system's problems concerning the heat is "It should shut down if it overheats". No answer to what happens if either machine is running just under the max temperature? Does this shorten the life span of the CPU/GPU? Not knowing this, to me, is really scary.
If some one knows the answer to the "safe" temperature, I would certainly like to be informed.
-Hugh D."

Based on reports, if it's overheating it would shut itself down (and sometimes that can cause freezes, etc.)T here's lots of reports here on observed temperatures (some higher than yours I think) but nothing that I have seen from apple on what the max temperature (inside the enclosure) of the design is. The only note from apple was on ambient (room) temperature spec.

(added 9/21/2005)
" I have an imac g5 17 inch with 1gb ram 1.8ghz processor. my mac would overheat reaching 98 degrees celcius (higher than anything i have read or heard) and continued to worsen. my capacitors were not bloated and my mac was in an open area. i tried to put a fan on it but that would not work. symptoms also include it forcing itself to sleep, a result of your thermal manager (recorded in System.log-type this into spotlight to find this easily), restart with a sudden blast from the fans that is overwhelmingly powerful, and internal fans were very loud constantly. I thought that was the way it operated.

i had read all about the video and power problems and how the overheating was the cause of that (my mac also falls into the serial number for these issues also). (He's talking about the capacitor problem mentioned earlier this year (reader article w/photos, etc.). Apple has a page on iMac G5 Repair Extension Program for Video and Power Issues-Mike) so i took it to the apple store. my logic board was the problem. this is an $875 fix if not under warranty.

i suggest that if your mac is overheating, not to try to mess with it and just get it to an apple store before your warranty runs out. now my mac runs whisper quite and it is a totally different machine. currently my temp monitor(bresink) says 56.8 Celsius and runs around 72 celsius with heavy video load. I believe that this should cut through all the hype about why they overheat. the overheating and any video/power issues are unrelated. i have read just about everything concerning this problem and feel confident that this will solve the imac overheating issues. a new logic board is $735. so dont wait around early imac purchasers!!!
-john a. "

If you have any problems (overheating, shut-downs, etc.) with any new Mac I'd have it serviced asap. Although John didn't believe that the overheating was related to the capacitor problem and didn't think the Apple repair extension program covered the "logic board" he had replaced I disagree. (The iMac G5's "Midplane board" is basically the main board/logic board of the iMac G5 - as mentioned in the past here. For example see this end user article on Replacing The iMac G5 Midplane Board which says "The midplane board is essentially the entire logic board, processor, cooling fans, input/output sockets and speakers...")
And for for those that don't believe that running hot can be related to the capacitor/midplane board problem - maybe you'll believe Popular Mechanics - their article on "Is The iMac G5 Running Hot?" noted

"Within a few months, we began to suspect a problem as, one by one, POPULAR MECHANICS's new iMac G5s started to overheat and then die. Eventually, 40 percent of them had to be sent back to Apple for repair or replacement. When we looked into the problem, we found a number of complaints about overheating power supplies and "bloated," apparently heat-damaged, capacitors on the midplane circuit board"

As mentined earlier this year - the Capacitor (type/brand) reportedly is the primary issue (the same issue was seen with many PC motherboards in the past) and although the Apple repair extension page does not mention overheating (it mentions power and video issues), the capacitors as far as I know are the root cause - and if/when they leak, it can affect the video/display as well as cause power related problems.
But again, regardless of the Apple extension repair program if you see any problems like this I'd contact apple for service asap. (Don't wait until it gets worse...)

(added 8/9/2005)
" Hi Mike, It's Matt Ruben again - thanks for posting my iMac G5 temperature story.
Another tidbit you might find interesting:
Tonight I burned a CD using Toast (6.1). (he has a 1.8GHz iMac G5 per his earlier report-Mike) I noticed the CPU temp had shot up to 172 F when the CD was done. I figured it's because CD- burning heats up the whole inside of the unit (burned CDs are always rather hot when the iMac G5 first ejects them).

But then the CPU temp stayed high, going up to 175. I set the CPU to "reduced" performance in Energy Saver, in order to get the temp down. It went down to about 148 F. I put the unit to sleep, left for about an hour, then woke it up and put the CPU back to "automatic" after seeing that the temp had gone down to 108 F while the unit was asleep. But to my shock it soon zoomed up to 176.3 F with the fans really winding up.

On a hunch I checked Activity Monitor and the Finder was using all available CPU cycles - 85-90 percent! And the temp was still rising. I called up the Force-Quit box in the Finder and Relaunched the Finder. The CPU temp went down to 150-155 F in a few seconds and now and then to 135 F in less than a minute. It's now at 128.7 F.

This could be somehow Toast-related, but the point is that my iMac would've constantly been running at 175+ F unless or until I logged out or restarted. Even sleeping wouldn't have helped.

I'm just wondering, since restarting the Finder is not the most intuitive thing, if this is the source of some people's problems - particularly those with Rev. B iMac G5s that don't have the capacitor problem.
Best, Matt"

(added 8/5/2005)
" Hi Mike, Just got my new iMac G5 today (stock 17" combo drive model). (1.8GHz model) I absolutely love it. Here's my CPU temp story:

Upon initial startup I transferred data from my old iMac G4. It took about 1-1/2 hrs (40 GB of stuff!). Then did Software Update (11 items!). Soon after I noticed the CPU was getting very hot - rear of iMac in that area hot to the touch, and Temperature Monitor Lite readings of 165 to 173 F. Fans would ramp up, pretty darn loud, and get it down to about 161-163. But then immediately the temp would shoot up again and the fans would ramp up.

Exasperated I set the CPU to "reduced" in Energy Saver prefpane. Temp went down to 147-149 F. Attempts to revert to default "automatic" CPU setting would result in 20 F spike in temp in about 5-10 seconds.

Finally, after running on "reduced" setting for a little over an hour, reverting to "automatic" did NOT produce the temperature spike.

Now, on automatic, the average temp is 147-149. I am getting spikes in the 155-165 area, but the temp quickly goes down to 155 or less even when the CPU is still busy.

So I think my machine is fine so far, but clearly a lot of CPU intensive work can drive the temp way up, and it can take quite a while for the insides of the machine to cool down.
(he later wrote)

I should also mention that the fans are very responsive to temp changes, but this responsiveness is also a little annoying - they're pretty quiet (except when temps get above 155-160 F), but they're pretty whiny sounding when they're in the process of speeding up.

In terms of the temps, since I first emailed you I've lived with the unit for a few days, with Temperature Monitor Lite always active in the menu bar. It appears the "default" operating temp is in the 135-150 F range. Sometimes, when the unit's been sleeping for awhile, it will wake in the 100-110 F range and operate in the 115-130 F range for a little while. But inevitably it will get up to the 135-150 F range. Running relatively CPU intensive processes like Windows Media Player (goodness what a CPU hog!), Photoshop and Mail (Mail's a hog only when first checking and filtering new msgs), the temp will get up to 155 F, and perhaps 165 F, but will settle back down towards 150 F within 5-15 seconds or so.

The only time I've seen sustained high temps was yesterday when Safari did one of its periodic annoying freak outs and started using 85-90% of CPU because it was on the point of choking on some Web site code. At that time the temp went as high as 174 F and the fans kept speeding up to get it down below 170 F. When Safari finally finished loading the offending Web pages that were driving it nuts, CPU use went down and temps gradually went down to the 155 F area, but it took a few minutes, and temps didn't return to the "normal" 135-150 F for quite some time.

So given all this, I would say that people are right that the iMac G5 design is sound but is based on very small tolerances in terms of heat. I would also guess that my unit is probably not one of the problem ones, and based on that I would recommend that anyone consistently seeing temps above 160 F under normal use should either turn on the air conditioning, call Apple, or take the unit in for a service check.
Hope folks find this info useful.
Best, Matt R."

(added 8/4/2005)
"Hi my name is Terence and I live Barbados.
The average day time temperature is 31.1 degrees celsius. This is not my first mac. My first mac was 700Mhz eMac I bought in the UK in 2002 and shipped back to Barbados in 2003. It logic board went literally in blaze of glory. A white flash, smoke, the smell of plastic components and a lot of melted plastic on the capacitors.

I bought my current iMac G5 second generation (2.0GHz G5, 17", 512MB of Ram, OS X 10.4.2) in June. I have downloaded a temperature monitor and it shows the average CPU temperature of 68 degrees celsius / 154 degrees Fahrenheit. Is my mac going into premature heat melt down? Or is the caribbean heat digesting my Mac? The power output in my country is 110V 50Hz. I need some answers. I put almost $1800.00 US in to this baby. Sure the warranty will not run out until June of next year but i do not like throwing money away.
-Terence A."

If you're that concerned about it - I'd ask Apple tech support (I can't say how long any iMac G5 will run personally and Apple would be the best source to ask about it since they designed it) - but you're reporting a lower temperature than some others reported here. A past post here said it was designed to run in up to 90F ambient temperature but I don't own one personally to check that.

(added 7/29/2005)
"Hi Mike, I have been running Temperature Monitor on my iMac G5 1.8 GHz for quite a while now. The CPU temperature is mostly around 65 to 70 degrees Celsius (I figure that for you this would read about 150 to 160 degrees Fahrenheit). When the CPU is really busy (for example gcc eats a lot of CPU time) the temperature gets as high as 80 degrees Celsius (about 175 degrees Fahrenheit).
The ambient temperature is dependent on the season from 20 to 35 degrees Celcius (about 70 to 95 degrees Fahrenheit) without any noticable effect on the CPU temperature.

In the FAQ on Bresink's site (author of hardware monitor) it says: "The maximum on-chip temperature for the PPC 970 is 85 degrees Celsius (158 degrees Fahrenheit), for the PPC 970FX it is 105 degrees Celsius (221 degrees Fahrenheit)." (Note: this is the internal CPU junction temperature rating - hardware monitor however is reading a sensor near the CPU, which means reported temps not the same as the actual internal CPU chip temperature.-Mike)

I had to read this twice, but I am getting absolutely no trouble whatsoever from my iMac G5 even during long compiler operations, when the system will run for half an hour or longer near 80 degrees Celcius (again, about 175 degrees Fahrenheit).
Regards, Florian P
(he later wrote) one p.s. ... A bit below in the same FAQ I cited in my last email it says: "This limit applies when directly measuring the on-die temperature. Because the sensors are often mounted in some distance from the processor and measure cache memory temperature at the same time, the displayed value can be higher than the value measured at the actual chip die."

This is mostly the opposite of what Tim wrote and what one would be expecting at first. But this is what heat-sink design is for, after all: guiding high temperatures away from heat sensitive areas ...

Though I do think it might be a temperature issue, since an additional fan seems to reduce the problems, I doubt that it is an issue with the CPU. Unless, of course, the G5 1.8 GHz in the Rev A iMacs is substantially different from the 2.0 GHz in the Rev B iMacs ... "

My gut feeling is that the iMac G5 was designed to not allow temperatures to exceed the CPU's rating, although I've always felt the actual internal CPU junction temperature was higher than the adjacent sensors report but I could be wrong in this case.

(added 7/29/2005)
"Take some of the heat off...
I have a new rev. B 20" 2GHz iMac G5 and run the temperature monitor to make sure my Mac stays cool after all the postings.

I have hads zero problems even though my iMac is in an enclosed cabinet. The average temperature running on "highest processor" performance is 155 degrees (F) with the Hard Drive at 123 degrees (F). The highest I have noticed was 177 degrees and if I set the computer on automatic setting, temps go down averaging 135 degrees.

I would like to know if there are any AC plug in fans that I might place in the back of the cabinet to lower the average temperature. One I can simply plug in the wall as an accessory.

I never hear my fans blasting but when I feel at the top back of my iMac I do feel a warm breeze. Thats as it should be.

I dont feel that its a widespread problem, but lets face it, the G5 chip runs very hot and that's why there are multiple fans on this iMac, thats why the iMac was delayed in coming out (rev 1) and it may very well be the reason my Steven Jobs decided to dump IBM for Intel.

The machine rocks and is by far the fastest, brightest and best running iMac ever built. With that comes some heat. A cool head my be in order because this machine is a perfect 10!
Stuart P. "

(added 7/29/2005)
"I have several iMac G5's. Even in very warm conditions I have not had any issues. Mine are all rev 1 iMacs, 1.6GHz and 1.8GHz 20" models. I have had times when fans kick in like Jet engines but the iMacs never stalled.
-Jon "

(added 7/29/2005)
"I too have an iMac G5 with an overheating problem. My first heat related kernel panic was in March and, not knowing it would later be a recurring problem, I ignored it. Then, in May, the problem kept getting more frequent. I updated to 10.3.9 which fixed the kernel panic problem, but only because it would shut itself down around 90 deg C. After some searching on the Apple k-base boards, I found the tips on checking the capacitors and also the suggested PSU replacement. I popped of the back - sure enough, swollen capacitors. (see Reader's article with info/photos on iMac G5 midplane board Capacitor problems in the July 7th news page-Mike)
My iMac was under warranty, so I had the PSU replaced (very quickly, I might add, less than 24 hours for the repair). Once the iMac was home, I went about my normal tasks at a still hotter-than-optimal 70-80 deg C. Fast forward a week and again we're seeing temps reach 90 and then shut down. I'm guessing caps need to be replaced now that the old PSU has had its way with them. Another theory is that the PSU replacement was just to remedy sleep problems with the shut-itself-down work around: after the 10.3.9 update, I was having problems waking from sleep.
The machine ran well for 6 months and was, I thought, one of the best Apple's ever produced. I've since changed my mind. I just bought an iBook which, I believe, is having logic board freak outs. Makes me think Applecare should be bundled with these things.
-Bryan "

Update: Apple has posted a page and FAQ on their iMac G5 Repair Extension Program for Video and Power Issues related to the capacitor problem mentioned earlier this year with some first gen iMac G5 systems. (July 7th news page has a link to a page w/photos and info) Here's a clip from the Apple page:

" The iMac G5 Repair Extension Program for Video and Power Issues applies to first generation iMac G5 computers that have video or power-related issues as a result of a specific component failure. If your iMac G5 is exhibiting any of the symptoms listed below and your computer's serial number is within the noted ranges, your computer may be eligible for repair, free of charge.
If Apple or an Apple Authorized Service Provider (AASP) determines that your iMac G5 computer is eligible as part of the program, the repair will be covered by Apple for up to two years from the original date of purchase even if your iMac G5 is out of warranty. This is a worldwide Apple program.

Affected systems will exhibit one of the following video- or power-related symptoms:

  • Scrambled or distorted video
  • No video
  • No power"
  • The page includes info on affected serial number ranges and answers to frequently asked questions. (Note - although the apple page doesn't mention it - one of the later reports above is from an owner that said his iMac was overheating and shutting down and that a midplane board swap fixed it. That's the board that is replaced usually (due to the capacitor issue).

    (added 7/29/2005)
    "Mike, we have had 4 out of 7 of our 1.8GHZ G5 iMac's completely fail and need to be replaced by Apple. With one we had an electrical burning smell. As a comparison we have 38 PowerMac G5's and 9 Xserve's, and not one has been replaced. We have stopped purchasing them.
    -Steve "

    (added 7/29/2005)
    "I'm a new owner (1 week) of a G5 iMac 20" (It's the latest Rev 2 Ghz model using 10.4.2)
    This morning I noticed my CPU temp was in the 135 degree F range and the fan was running continuously and loudly.
    I used the process monitor to see what was running and found the 'Stickies' widget was eating about 85 percent of the CPU. I had a single Stickie open and had some text on it.
    I quit the Stickies widget and the temp is down to 105 now and the fan is just barely audible.
    All other programs/widgets are in the same state as when I quit stickies.
    Ambient temp in the room is 73 degrees F
    -John "

    (added 7/29/2005)
    "Hi Mike, I've just brought an iMac G5/2ghz 20" machine nearly 1 month. Beforehand, my friends told me that 17" model does have heat emission problem; the machine fan almost runs high speed even just surfing the web and playing iTunes. It may be due to smaller space which does not provide enough space for air ventilation. Finally, i get a 20" model.
    The 20" model is nice and surely quiet.
    The fan speed has never turned to full speed; unless i start it to target mode (firewire target disk mode) to connect with other Macs.

    The highest cpu temperature recorded is under WarCraft III playing. Apparently, the fan speed is turning faster under 100% cpu usage, however, it is not the fastest I've met.
    Once I quit WC3, the cpu temperature dropped quite fast, about 20C lower within 1 minute. Actually, I don't think my iMac G5/2ghz 20" model has an overheat problem.

    Besides, I have tried two temperature monitor software: ThermographX and Temperature Monitor. From the enclosed screen captures (too large to post here), you can see that there is about 4 degree Celsius different of two softwares (reporting). There is about 82C reporting by ThermographX while Temperature Monitor reporting 77.5C...
    regards, Ronny "

    I've received a mail from an iMac G5 1.8GHz model user on overheating/shutdown problems in heavy use even in cooler ambient temperatures:

    (added 7/28/2005)
    " I'm having consistent problems with overheating on my 1.8GHz G5 iMac when using it with Final Cut Pro. "Temperature Monitor" reports CPU temperatures up to nearly 90c (190F) at which point the machine shuts itself into sleep mode. The fans are mechanically fine, but never run up to full speed. It appears as though the software is not controlling them properly.
    This is with ambient temperatures of only 20-21c

    (in case this is a fan control issue addressed in a future update, I asked what OS version he's running and if he'd contacted Apple about the problem-Mike)

    Apple are being somewhat obstructive about this... I've had the problem since 10.4.1 and now 10.4.2, recently installed the 'sleep light' update too... More on a hunch that it might poke around in the firmware to some helpful end than anything else.

    When I get the opportunity I'll knock it back to an older OS. I seem to have two side by side temperature issues though:

    Sometimes the machine will shut down fully with a 'pop', and the 'overheat' LED remains unlit. I take it this is the PSU's internal over temperature protection kicking in.

    Other times the imac will just sleep spontaneously; in these instances the LED does illuminate red for a temperature problem, so I'm also assuming this is the processor going over temp.

    Once in a while it'll do a combination effort and I go for a long cup of coffee :)
    John M.
    KipperTie Ltd
    Apple Solution Experts "

    Another reader replied to this post:

    (added 7/28/2005)
    "At my work we have 3 iMac g5s. 2 of them had "overheating" problems where they would turn off in the middle of use. I used to work at an apple authorized retail shop, and a friend of mine in the repair center told me that it was happening a lot. He also said that it was from bad power supplies. One of ours smelled like burning plastic the day before it started to do turn off on its own, so I kind of knew it was coming. The faulty supplies are getting so hot, that they are actually melting some of the heat shielding. If possible, I recommend that the people with this problem call apple or take it to an apple store.

    There were past notes here on some iMac G5s having capacitor problems (capacitors that eventually swelled or burst - see Reader's article with info/photos on iMac G5 midplane board Capacitor problems in the July 7th news page) but I thought that issue was not a problem on the later builds.

    For other Systems related articles, see the Systems page (organized by mac model/series).

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