starts to boot up, screen goes white, then black and then starts to boot up again. This process repeats itself several times and then I give up and power the Mac off. It is about 10 years old and would love to be able to use it as a monitor only. any ideas?
iMac 27″, macOS 10.13
The 27" iMac has user accessible RAM modules. It may be that one of them is failing.
Install memory in an iMac: https://support.apple.com/en-us/HT201191#2
I would remove all of the RAM modules that are installed in the iMac.
Then I would replace them all back, making sure they are seated snug and proper, and try to restart the iMac.
If the iMac still fails to restart, then I would remove the RAM again but this time reinstall them, one at a time, and try to restart the computer after each. If you can get the iMac to restart with a single module in it then you're making progress. Of course some iMacs won't restart with only a single module in place so that could be a factor here.
Also, since you can't get the specific year info from the iMac itself, you might visit everymac.com at this website: https://everymac.com/ultimate-mac-lookup/
There you can type in the serial number found on the bottom of the iMac and look up exactly which machine it is.
The 27" iMac has user accessible RAM modules. It may be that one of them is failing.
Install memory in an iMac: https://support.apple.com/en-us/HT201191#2
I would remove all of the RAM modules that are installed in the iMac.
Then I would replace them all back, making sure they are seated snug and proper, and try to restart the iMac.
If the iMac still fails to restart, then I would remove the RAM again but this time reinstall them, one at a time, and try to restart the computer after each. If you can get the iMac to restart with a single module in it then you're making progress. Of course some iMacs won't restart with only a single module in place so that could be a factor here.
Also, since you can't get the specific year info from the iMac itself, you might visit everymac.com at this website: https://everymac.com/ultimate-mac-lookup/
There you can type in the serial number found on the bottom of the iMac and look up exactly which machine it is.
It would help to know exactly which iMac model and year this is.
Try to restart the iMac in Safe mode.
How to use safe mode on your Mac - Apple Support
Press the power button and immediately press and hold the shift key until you see the Apple logo and progress bar.
To be honest, I'll be surprised if you can get this to work, but it's worth a shot.
27” iMac about 10-12 years old.
iMac will not boot up
