The fan don't stop
Hi, I have an old Mac mini Core Duo 1.6mhz with a zombie problem.
I would guess, it's not dead, but either a life.
If you just plug the power supply, after 3 seconds, the fan starts like crazy. There are no lights on, no video and you can't turn off the machine. The only option it's to remove the power cable to turn it off.
The problems happen with the hard drive sensor cable plugged or not puggled into the motherboard.
I also tried resetting the SMC manager in many ways. Like, taking apart the machine and removing the clock battery.