# [SOLVED] iMac g3 shuts down after being on for 5 seconds



## seantobin5 (Jun 2, 2008)

Hello, I have an iMac g3 i decided to fix up but when i plaug everything in and hope everything will go good, it shuts off after about 5 seconds. heres what it does: 1. Apple chime
2. monitor seeme to be turning on
3. hard drive spins up
 4. Hard drive parks and shuts off
5. nothing happens and the monitor is off but the green power light is on. 

Heres what I've done with it so far: I've out a new backup battery into the logic board, I've also put another hard drive inside it. I hopr you guys can help me with this! Thanks!


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## macthorough (Jul 5, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

Seem's like the iMac cannot find the OS. Can you boot to a CD? What OS are you trying to install?


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## seantobin5 (Jun 2, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

i wiped out the OS on my iBook and i tried to install OS 9, and OS X 10.3. it wont boot from the CD and I did press "c" at startup.


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## macthorough (Jul 5, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

Is the computer beeping at you with 3 beeps? If so look at ram.

The fact you cannot boot to a disk indicated a hardware issue.

Boot into single user mode and type fsck -fy

(include the spaces and boot into single user mode you hold command + S on startup)


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## seantobin5 (Jun 2, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

The computer is not beeping at me and there is 192 mb of ram. also, i could not boot into single user mode. i also noticed if i press the reset button 3 times prior to when i first turn on, it just shuts off in 5 seconds. I ope you know what i mean... i think it may have something to do with the power supply. is there a fuse I should replace?


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## sinclair_tm (Mar 11, 2005)

*Re: iMac g3 shuts down after being on for 5 seconds*

What OS was it running when you got it? Do you see any picture on the screen before it turns back off? Have you tried to reset the PRAM, allowing to chime three times? To do that, turn the Mac off, then turn it back on, as soon as you hear the chime, hold down these 4 keys, and keep holding them down until you hear the chime at least 3 more times, command-option-p-r. Were you able to get it to install and run OS 9 fine? Can you boot from a CD? Did it start acting up after you installed OS X?


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## seantobin5 (Jun 2, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

A friend gave it to me a while ago and I don't know exactly what OS it was running but im pretty sure it was OS 9 because it broke down in 2002. and i only hear the screen starting up but theres no picture on it. and i also tried command option p r. also, i cannot boot from the cd i put into there.i presses "c" at startup. could it be a power supply problem? and how do i get into the power supply?


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## macthorough (Jul 5, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

it could be power related but you want to see if you can boot to single user mode, startup manager, or open firmware... if you can boot to these, then you can most likely reinstall...

if you cannot you have something wrong with your HW... mac os x needs 128mb ram to install so you're good there. you need 1.2gb of available space.

you power supply could have a short but that is not probable. It seems like there is a bad connection somewhere. 

also make sure you are installing with a proper install disk. you cannot install with a powerbook or ibook disk... you should try to obtain a retail copy of OS 9, 10.2 or 10.3.


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## seantobin5 (Jun 2, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

I cannot boot into single user mode, so it must be a hardware issue. I also have the retail version of OS 9 and 10.3. But it shuts off before the cd drive even starts to spin. I'll just crack open the imac and check back when it boots up! thanks!


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## sinclair_tm (Mar 11, 2005)

*Re: iMac g3 shuts down after being on for 5 seconds*

Did you update the firmware before installing OS X? On G3 iMacs, you had to update the firmware before installing OS X, or else it would brick the iMac. And I have a feeling that is what happened here. You said that the monitor light stays on, but the screen remains off. Read here, and hope it points you in the right direction.


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## seantobin5 (Jun 2, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

well, the hard drive shut off before I can do anything with it. I got into it and I'll see if replacig the fuse will help at all.


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## seantobin5 (Jun 2, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

just wondering, how do you reset the PMU on an imac? i dont wanna know how to reset the pram cuz i already did that with no luck... Thanks!


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## seantobin5 (Jun 2, 2008)

*Re: iMac g3 shuts down after being on for 5 seconds*

i looked throught the imac today and found a VERY fine crack. so well, thanks for all your help guys!


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## sinclair_tm (Mar 11, 2005)

I take it me mean a crack on the motherboard? That would kill it alright. 

As for resetting the PMU, that is only on laptops, as it's the unit that controls the wall and battery power settings.


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## macthorough (Jul 5, 2008)

sinclair_tm said:


> As for resetting the PMU, that is only on laptops, as it's the unit that controls the wall and battery power settings.




PMU <===Click here

PMU <===Click here

Haven't you ever heard that saying Crack Kills???


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## sinclair_tm (Mar 11, 2005)

That's not the PMU reset, it's the CUDA switch. To be technical, it is a PMU for the desktop Macs, but as for the involved Mac of this post, PMU is for laptops, and CUDA is for desktops. But onlike laptops, where resetting the PMU is a common pratice, resetting the CUDA on desktops isn't something you want to do unless you have tried everything else, short of replaceing the motherboard, as it has been know to cause more havoc than the original problem.


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