iMac won't turn on unless I remove and reconnect power cord

Try resetting the SMC: http://docs.info.apple.com/article.html?artnum=303446

I had this same problem with my G4. I had just installed Leopard and spent a lot of time messing with my system. Thinking it might be a bad front panel board (connected to my power button). We had to press the PMU button on the logic board. It may have been one too many times because my G4 is now DEAD. Logic board went bad, or did I have help with that?

I bet if you search this forum you'll find many a Mac user with this problem not realizing those who have other Macs have the same problem. Why do I think this?

I'm not sure why my computer wouldn't reboot unless I reinserted the power supply but, I have swapped out different power strips, outlets, even different circuits. Then I purchased an APC UPS Backup. G4 died. A friend of mine loaned me his iMac and guess what?

The old problem is BAAAACCKKK! I'm connected to the UPS but if I shut down, the power button on the back of the iMac will not work unless I unplug and reinsert.

What is going on? Hope you found a solution. Please share.

Hey myhighway,

I disconnected everything. Let it sit. Booted via the power button (which is never a problem the first time). Then I Shut down. Rebooted via button with no problem. So perhaps there is something to this, at least for the iMacs.

Saving my money for a MacBookPro. Hoping to hear Steve announce an even faster one on the 16th at MacWorld. I wanted to make sure my electrical in my office didn't fry my friends computer or my next new Mac. Well, I have a nice APC UPS which is a good thing. Thanks.

When I started out my problems all seemed to begin when I installed Leopard. I thought that it was an OS problem (first I had other issues: my 2 optical drives were not visible and startup disk selector was not letting me switch booting to other drives). But soon I discovered that shutting down caused me more problems than anything else. I still cannot pinpoint what exactly started it all but definitely want to make sure I don't mess up this borrowed computer. (iMac 2.16 GHz Intel Core 2 Duo). Good luck to you.

Its me again...well, I think I have found the problem, its called "time machine", if I Turn on my external firewire HD (where time machine does the backups) it wont turn off completly (unless I disconnect de power cable), but If I never turn on the HD the Mac turns off normal.

I think I will go back to 10.4 until 10.5 become stable.

Message was edited by: Eduardo Capdeville

if I Turn on my external firewire HD (where time machine does the backups)...

Is Time Machine a matter of "if"???

How can Time Machine truly work if you don't have it connected ALL THE TIME?

There's nothing wrong with Time Machine.

Well, I can say that Time Machine is guilty...

Test 1
a.- Firewire HD configured to use Time machine
b.- Time Machine working
result.- Mac wont completly turn off and at the same time wont turn on later.
fix: disconnect power cable, then everything becomes normal

Test 2
a.- Firewire HD on
b.- Time Machine disconnected
result.- Mac turns off normaly, will turn on with the power button

-------
So, Time machine is making crazy the "off" routine...I better wont use it.

please 10.5.2!

I think I would agree with it not shutting down completely (For whatever reason). Mine is doing the same thing. But in order to turn mine back on, I hold the power button down for a while (like doing a force power off) then I press it once and it boots up. I have not tested disconnecting my Time Machine backup drive though (USB).

I had exactly this problem. I fixed it by booting the machine with all peripherals removed except the keyboard and mouse. I then shut the machine down and reconnected the peripherals. The computer starts quite normally now.

Hi there I am not too sure that Time Machine is responsible, as I don't have it installed on my system, I started to experienced this issue after upgrading to 10.5.2 first I had a painfully slow start, with my iMac taking over 5 mins from startup chime to login screen. Then now everytime I shut down my system the only way I can get it to restart is by unplugging it from the main first. I have tried to rest System Management Controller but I wasn't very successful.

I run disk utilities and everything was OK

So I guess until I found a fix to my slow start up and now unplug before you start I have no other choice but to put my system to sleep. ( not so good for the environment, and my CO2 Footprint ..... Doh .....)

If anyone has experienced these faults after update to 10.5.2 and find a fix email THX ...

*Hi Lost..., Welcome* to Apple's Users Help Users Forums. 🙂

This is an old solved thread. You will get better service as you deserve by posting a new thread.

Good Luck, JP 🙂

Message was edited by: Jpfresno wrong name

Check out the advice in the last Peggy Lynn post of Jan 15, 2008 2:13 PM

http://discussions.apple.com/thread.jspa?messageID=6342001&#6342001

Hey pcgs:)

How many days use did you get out of the loaned iMac until this first happened? The SMC reset has had no effect?

Probably a couple of days. I recall booting at least twice without problem. Any ideas?

I will attempt the SMC now and post my findings.

Message was edited by: pcgs