Chosen Solution
Unit will work for days fine then at power up doesn’t boot to hard drive but to question mark. I have reselected start up disc. If I boot holding shift key I can get it to boot to hard drive ok.then will work for a week or two then same. Now first time locked up while unit on and had to force shutdown. No sign bad caps in power supply very familiar with. Bad hard drive or system board? Or is this model with other known issues
Bad hard drive. Either replace it or boot from an external source reform the drive using the “write zeros” option the map out any bad blocks. Or do an internet install. Better would be to replace the drive with an SSHD hired drive. That drive is seven years old now. Here’s how: iMac Intel 24" EMC 2267 Hard Drive Replacement Here’s a good drive: 1 TB SSD Hybrid 3.5" Hard Drive
