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Travis, Mac-Trained Product Designer
Category: Mac
Satisfied Customers: 759
Experience:  19+ Years of Mac Experience, BSA in Design and 6 Years of Mac Training from University of Cincinnati
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IMac turns on but then turns off

Resolved Question:

My iMac keeps trying to power up, but then just shuts down after two seconds. The farthest I get is hearing the HD trying to ramp up, then quickly powering down. Nothing happens on the screen.
It was working fine; I walked away from the computer for about an hour, when I came back, it was stuck in this cycle of attempted boot ups. What should I do?

Submitted: 6 years ago.
Category: Mac
Expert:  Travis replied 6 years ago.

Do you know what may have caused the issue?

I would first, before you do anything else, unplug everything from the iMac. Unplug EVERYTHING, all cords, power cord, USB, Firewire, mouse, keyboard, everything. DO NOT touch any of the power buttons on anything while it is unplugged, or while plugging it back in.

Leave it all unplugged for 20 - 30 minutes. The plug it all back in, and try to turn it on again. This should reset the system management controller and may reset the power issue.

If it doesn't work, there may be a different process for your specific machine. What type of iMac is it? Is it Intel or PowerPC? How old is it? What size monitor does it have?

We'll go from there and get you up and running again.

Customer: replied 6 years ago.

I'm not sure what would have caused the issue. I had the comp on in my office. I turned it on, and it started as usual. I did a few hours of work, word processing, a little internet browsing. I left the office for about an hour, leaving the computer on, but I normally do that and have never had a problem. I have the whole thing plugged into a surge protector, hoping that would prevent it from frying, at least a little.

I have the 17" iMac; I bought it about 2 years ago. I'm not sure of the processor.

I am currently trying your suggestion of unplugging all cords and such and will retry it in another ten minutes or so.

Expert:  Travis replied 6 years ago.

Are you able to locate the serial number on the iMac? This will be able to tell us if it is an Intel or PPC.

Customer: replied 6 years ago.

Serial #: W88252CLZE3

I tried restarting and got a little further, grey apple screen came up, then got stuck on the blue screen. It powered down, restarted, did the same thing. The third attempted boot it did left me with the black screen, the grey apple screen didn’t pop up at all again.

Do you have any suggestions?

Expert:  Travis replied 6 years ago.

Before we go any further, I would suggest you start using a program like Carbon Copy Cloner ( to create a restorable backup of your Hard Drive to an External Hard Drive. This free program will make a mirrored copy of your hard drive in its current state that you can go back to if things go south for any reason. I do this personally before I perform any kind of install, update or major change to my system. Then if you find yourself in this type of situation, you aren't as frantic. BUT, you don't seem to have a backup right now, so let's get your machine up and running, shall we?

Do you have access to another Mac? If so, now would be a good time to try to connect the two machines in Firewire transfer mode, that way you can at least get your important stuff off of the machine if it is able to boot up into Target Mode. If you do have another Mac close and an Firewire cable to connect the two, I would try this first.
1) Shut down your troubled Mac.
2) Start up the good Mac.
3) Connect a Firewire cable between the 2 machines.
4) Press and hold the T button and then power up the troubled Mac. Don't let go of the T until the Firewire logo starts bouncing around on the screen.
5) This should connect the troubled Mac to the good Mac as an external hard drive.
6) You should then be able to backup the troubled Mac to another external drive or to the good Mac via Carbon Copy Cloner.

If you don't have access to another Mac or the Transfer mode startup didn't work, then try the following:

Hold the "X" key during startup immediately after pressing the power button (Don't let go until it starts from the disk or locks up). This may force the computer to start up to Mac OS X. If it does, open System Preferences and be sure that your Mac OS X System Folder is selected. If this works, restart after you have your startup volume selected. If this corrected the problem, STOP HERE. If not, go on to the next step.

1) Restart while holding down the Option key immediately after pressing the power button (Don't let go until it starts from the disk or locks up). This should bring up the Startup Manager and would allow you to select the startup volume. It may work if the computer is stuck, and can't find the correct startup volume! If this works, open System Preferences and be sure that your Mac OS X System Folder is selected. Restart after you have your startup volume selected. If this corrected the problem, STOP HERE. If not, go on to the next step.

Follow the steps below and let me know what each one yields.

1) Unplug everything (iPod, USB hard drive, printer, etc) except the mouse and keyboard from the computer. Then restart. Does the machine boot up or get stuck again? If it starts up, plug each thing back in one at a time, restarting the machine each time until it locks up. Remove this item and continue adding items until you have everything plugged back in that you can and still have the machine restart successfully. Let me know which peripheral(s) locks the machine up.

2) Plug everything back in (but make a note of what caused problems for later troubleshooting). Start up the computer in safe boot mode. To do this, press the power button. As soon as you hear the startup sounds (immediately after you hear the sound, but not before), press and hold the Shift button. Let go of the Shift key as soon as you see the gray apple icon and the progress bar (or wheel). Does the machine boot up or get stuck again?

3) Insert the Mac OS X install disk. Start the machine while holding the C key immediately after pressing the power button (Don't let go until it starts from the disk or locks up). If you have to choose, select the Installation disk as the startup. When it starts, cancel the Installation process. Then go to the Go menu, down to Utilities. Choose the "Disk Utility" program. Run Disk Utilities. Select your hard drive in the column on the left and "Verify" the Hard Drive. Repair any errors that it may find by next choosing the "Repair" button. When finished, restart the computer normally. Does the machine boot up or get stuck again?

4) While the computer is shut down, locate these keys: command (has an apple on it), option (sometimes called alt), P, and R. Turn the computer on, then press and hold Command-Option-P-R before the gray screen appears. Hold these keys down until you hear the startup sound a total of 3 times. Release the keys. This resets the PRAM on the machine.

5) Startup the computer normally (not off of the Install CD) with everything plugged in. When (if) the machine starts up, go to Applications / Utilities / and run "Disk Utility". Choose the Hard Drive on the left, and then click the Repair Permissions button. This may take a while. When finished, quit Disk Utility.

6) Restart normally.

Customer: replied 6 years ago.

I can get to another Mac sometime tomorrow. Will that work? Should I try any of the other suggestions first?

Expert:  Travis replied 6 years ago.

I would say at this point, if you have important stuff on the machine, I'd try to connect it to another Mac first. However, to save time, I'd suggest seeing if it WILL start up in Target mode first. If it won't then I'd go ahead with the next steps. If it will start up in this mode, then I'd wait until tomorrow.

To test it, hold down the T key and press the power button. Keep the T down until it either freezes or the Firewire logo pops up. If it freezes, then move to the next step (no sense in waiting until tomorrow). If it pops up the Firewire logo, then shut it down and wait until tomorrow.

Travis and 3 other Mac Specialists are ready to help you
Customer: replied 6 years ago.

I got it to start in Target mode.

Customer: replied 6 years ago.
Thanks Travis.
It took me a day or two, but I managed to back up the files I need, and the computer is turning on now.
Thanks for the help