Over the last couple of days, my PC when starting up from cold displays CPU Fan Error - Please F1 to go to Setup.

Now, I will make it perfectly clear that my Desktop has not had a new Fan fitted since it was built in August 2014. Nothing has been touched or altered after it was built.

Anyhow, after you going to BIOS setup and then exit; the PC boots up as normal. You can close it down and restart it again as normal without any error message. I left it for about an hour to clear down and rebooted it again and error never appeared. Then I left it overnight and booted it up, the error message appeared again.

I have ensured that there is no dust in or around the Desktop just in case things might be getting too hot, plus in the BIOS screen, I changed the setting for CPU from Standard to Full Power. Using hardinfo in Ubuntu, the CPU temperatures when the OS is at idle are around 27-30 degrees, it doesn't shoot up to say 80, and I deliberately did this from the OS and not from UEFI BIOS screen as this will give a completely different reading.

The basic details of the machine are:

Intel Core i7.4790K CPU at 4GHz Asus Z97P Motherboard with 32GB of RAM.

So, I have two questions:

Is this a problem with a faulty fan, and if so should I replace it? Or is it a problem with the motherboard, which is a sign of a much bigger problem lurking round the corner?

If it is not a problem - I do make the message go away? As I say it only appears after the PC has been left after a massive amount of time. Should I be worried?