My grandfather's PC was shutting itself off, and based on my previous inspection, I thought it could have been a bad PSU, since the PSU fan was barely spinning, while the CPU fan was working fine. So, I ordered a new PSU (a Cooler Master GX 450W), which should arrive soon.
However, I decided to disconnect and reconnect the PSU to the mobo, and now the PSU fan works fine, but the CPU fan isn't spinning at all. Perhaps I was thinking the PSU might have shifted its power from the CPU fan to its own fan.
So, what you think the problem could be - the fan itself, the PSU, or the motherboard? The motherboard is a Gigabyte GA-8IG1000MK, and the current PSU is a cheapo Dinamax 450w model.
I really hope it isn't the motherboard. FYI, at least the motherboard does seem to detect the fan not spinning when I enable the CPU Fan Fail Warning in the BIOS, so hopefully this is a good sign. I already ordered a new PSU, but if the fan itself is the issue it shouldn't cost much to buy.
Someone will be lending me another fan to see if that is the issue. Either way, I already bought the a Cooler Master GX 450W PSU which should be arriving here soon. If the issue isn't the fan, hopefully it is the PSU and not the motherboard.
It appears the problem is in the +12v rails that provide power to the fans. (Assuming the CPU fan didn't suddenly decide to go bad). But since the PSU fan was problematic and now the CPU fan is problematic, I would say the PSU is the most likely culprit. A PC that shuts down by itself is usually PSU related. Since you have a new PSU coming, you should have the answer soon.
Just installed the new PSU, no luck. I really hope it is the fan and not the motherboard.
EDIT: I don't know if this means anything, but to test if the fan is bad, I decided to test the CPU fan in the system fan header. As with the CPU fan header, the fan does not spin in the system fan header. Could this be a sign of a bad fan?