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When i turn on my iMac G5 (2006 model) , the fan runs really

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When i turn on my iMac G5 (2006 model) , the fan runs really loud after about 30 seconds, there is no startup chime, and the screen doesn't light up/no video, but the white operating light comes on solid. I have tried resetting PRAM but holding down contorl option P R keys doesn't do anything different - no startup chime, white light solid, after 30 secs the fans come on, black screen remains. This happened about 3 times before in the last week, but I simply pressed the power button off, waited a minute then restarted and Mac booted as normal. i also tried Target Mode to my MacBook G5, but the iMac never went into firewire mode and did not show up as a drive on my host MacBook G5. The Apple tech note on troubleshootng this doesn't say what to do if the PRAM reset doesnt work... should I try starting up from the original G5 install disk 1? I'm concerned the Target Mode Firewire failed as well, at least I could back off the HD data... Any ideas?
Hello, and thank you for asking your question, with
I am Sr. Mac Tech Support Specialist, Terry, glad to assist you.

Here are some steps you can try to resolve the issue:
First to help you in properly identifying the models of Macs that you have,
neither the iMac (2006) or the Macbook are G5 models. the G5 or Generation 5 models of computers were made with the PowerPC processors.

What you have now are the Intel iMac (2006- I have one of these as well) and simply the Macbook (also has 2 Intel processor chips built on its board). I wanted to make this clear for you, in the event you have to take your iMac or Macbook in for service or make a call for service, the service center will know what you are referring to.

Now here is a simple process I would like you to attempt to see if we can resolve the Fan issue:

The System Management Unit is an integrated circuit (computer chip) that is usually on the logic board of your Mac computer.

It is responsible for power management of the computer. It controls backlighting, hard disk spin down, sleep and wake, some charging aspects, trackpad control, and some input/output as it relates to the computer sleeping.

• If the computer is on, turn it off.
• Disconnect all the connections going into the Mac except for the Power cord.
• Once all connections have been disconnected, remove the power cord from the
• Wait 30 seconds.
• Reconnect the keyboard, mouse and power cord back into the computer.
• Press the Power button to restart the Mac computer.

Let me know if it boots up normally or not.

I wil be watching for your reply. Thanks!


Customer: replied 7 years ago.
Hi Terry... the manual says this is an iMac G5, maybe 2005 not 2006 model? It's running OS 10.4.11. Still no luck on that reset - no chime, screen stays black the white light is on at about half power.... after approx 20 secs, the fan comes on full blast.... should I go ahead and shut it off?

thx, Haylie akaCustomer
Oh ok thanks for that clarification Haylie, then an iMac G5 it is.

Yes that is fine go ahead and shut it off.

There is one procedure I would like to have you try, just to check the integrity of your hard drive.


Start up your computer in Single-User Mode to reach the command line by doing this:

•Make sure your Mac is shutdown.
• Reboot your Mac
• When Mac starts up, press the Apple Command key+ S Key
- A black screen, with white text appears
• At the command-line prompt, type: /sbin/fsck -fy
• Press Return.

--fsck will run through a series of tests and will return information about your disk's use and fragmentation. When completed, it will display this message if no issue is found:

The volume (name_of_volume) appears to be OK

If fsck found issues and has altered, repaired, or fixed anything, it will display this message: --FILE SYSTEM WAS MODIFIED--

Important: If this message appears, repeat the fsck command you typed at the beginning, until fsck tells you that your volume appears to be OK (first-pass repairs may uncover additional issues, so this is a normal thing to do).

• When fsck reports that your volume is OK, type reboot at the prompt and then press Return.

• This last command after completing the fsck process, is going to attempt to boot your Mac to the main desktop.

Keep me posted I will be watching for your update. Thanks!

Customer: replied 7 years ago.
Hi Terry, there is no startup chime, holding down the keys for anything has no affect whatsoever, I held down for 30 secs, then release, and the fans come on full blast.... when there is a chime, typically you would hold keys after the chime, but with no chime ?? should I wait until white light comes on or ?? Do you think Keyboard or mouse is failing, I probably have a spare I can swap in...
Actually Haylie, if you are unable to perform an fsck repair, then that means there
may be an issue with the Mac OS X volume of your hard drive.

Now, this does mean that you have lost your data on the hard drive or the hard drive itself; it just means something may be wrong with the Mac OS X system software on the hard drive.

So at this point, what I do need to know now is do you have the Mac OS X 10.4 Installation disc that came with your IMac G5?

I will be waiting for your reply once again.

Customer: replied 7 years ago.
I tried swapping in another mouse that I know is working, the other plugin mouse was quite old (i also have a bluetooth mightymouse that I use instead of the plugin mouse) and that made no difference. When I hold in the on button, it makes a click like it usually does and the light turns on and then there should be a start up sound but nothing happens... and then 20 secs later comes the fan...

Did you mean to say Now, this does [not] mean that you have lost your data on the hard drive or the hard drive itself; I hope!!

I do have the original disks, it came with 2 Mac OSx install disc 1 and Mac OSX install disc 2. And a Mac OS X Tiger disc markec CPU drop in to DVD.
Customer: replied 7 years ago.
I tried swapping in another mouse that I know is working, the other plugin mouse was quite old (i also have a bluetooth mightymouse that I use instead of the plugin mouse) and that made no difference. When I hold in the on button, it makes a click like it usually does and the light turns on and then there should be a start up sound but nothing happens... and then 20 secs later comes the fan...
Thanks for that update and information. That is good. Considering you have
Mac OS X Tiger on your iMac, I will need you to insert the Mac OS X install disc 1 in the drive of your Mac.

If you are able to do so, I would like to see if I can help you boot that install disc up to the Installer environment where you can run a Disk Repair using Disk Utility.


Insert your Mac OS X Startup disk
•Reboot your Mac
•At the Apple Chime, press the C key and hold it until you see a White screen, gray Apple and eventually a Spinning gear.
• Release the C key only after you see the Spinning gear.
•Mac will boot from the startup disk to the Installer environment
• From the Installer Menu bar, click Utilities > Disk Utility and open up Disk Utility application.
• Click on on the hard drive at the top of the window in the left sidebar and
• Select "Repair Disk"
**Let Disk Utilities run this repair the disk until completion
• At the end of this process, reboot your Mac

Let's hope you can get this far. I will be watching for an update from you regarding this procedure.

Thanks so much for your patience!

Customer: replied 7 years ago.
Hi Terry, other threads I can find on this exact problem - it appears to be a common one - indicate a logic board or battery failure or soe other hardware issue

i have a call back due from Apple tech at 8:15a and an 8:45a appt at Apple Store genius bar (this is my production mac, i'm a web dev) so all I really need to do is get it to a place where I can back off the data - is it worth trying the boot from Install Disk or do we risk damagign the data that is left on the HD?

I'll accept the payment for all your help, but no need to keep thrashing at this if the techs just have to take it apart in the morning (which is like 5 hours anyway :-0)... If you think it's safe to try the Install Disk I'm game to try it, as if it won't boot from the CD then I guess it is another clue in the troubleshooting puzzle...

If I click Accept will it end this thread? Don't want to do that until we sign off here.. but I will pay! :-)

Hi Haylie, I know. In fact I was trying, just hoping that it would not be the case that this was a hardware issue. What first struck me as a more a possible logic board issue, was when the fsck command failed.

There would be no hard to your hard drive if you attempt to boot from the install disc however, because performing that procedure takes the responsibility of booting up from the hard drive and places it on the install disc. This is a normal diagnostics process that we Mac techs use more often than I can count. Apple has designed it this way so a diagnosis and potential repair of the hard drive, can be attempted.

You are welcome to still attempt to boot to the Mac OS X Install disc as I had suggested, because this was actually my last effort to see if your iMac woud at least boot to the disc. If it does not, then I was already prepared to let you know, this is a potential hardware issue, more than likely with your logic board or hard drive.

I am glad you have already been proactive to setup an appointment with an Apple retail store Genius bar. That would be the next course of action I would recommend.

I leave it to your discretion to Accept and this point. But know that the post does not immediately close after an Accept, so if you should come back and reply to the post, I will make sure I reply back to assist with any other questions you may have.

Thanks so much Haylie for your patience and in allowing me to assist you with this issue.

Sincerest Regards,

MacTechTrainer and other Mac Specialists are ready to help you
Customer: replied 7 years ago.
HI Terry, I'll go ahead and Accept and close this ticket and hopefully I can bribe the Apple techs into salvaging my harddrive so i can back off the data if I buy a new iMac tomorrow, lol! THis has been a production Mac in constant use for 3+years, so I guess I'm not surprized, tho i have had Macs since a Mac plus in 1986 and tho they're all here in storage all of them still work - first time I've had a logic board failure -- than the usual failed power supply issues. Thanks so much for trying though! This is a cool service, and nice to know it's here next time I have a Mac tech issue! Thanks again! Haylie
Thank you for the Accept. I hope the information I provided you, has helped you to point you in the right direction.

Please feel free to reply again, if you still have questions regarding the question I just answered for you.

Thank you again!

Sincerest Regards,