Pc won’t display but fan runs loud

 Loud computer fan happens when your computer is generating a lot of heat, which causes your computer’s fans to leap into action, forcing the hot air out of your PC so that cooler air can cycle in. Loud computer fans can also be caused by dust building up in your PC, which negatively impacts its performance.

Inside your computer is a lot of sophisticated hardware — your CPU, graphics card, power supply, and more. These all generate a ton of heat. And the sensitive electrical components inside your PC are vulnerable to high temperatures. To keep heat levels down, the fans inside your computer start spinning to push the hot air out and cool down your PC.

Loud computer fans and loud laptop fans can indicate problems, especially if the noise persists for a long period of time. A computer fan’s job is to keep your computer cool, and excessive fan noise means they’re working harder than they normally need to.

There are several ways to address desktop or laptop fan noise to quiet your computer.
Each of the following tips should help clean up and boost your computer performance considerably. Try them in order — if one doesn’t work, move onto the next.

1. Make sure cool air can reach your computer

Before we get to your computer’s internals, make sure you’ve placed your computer in a location that helps it cool down.

Place your desktop (or laptop) computer on a smooth, flat surface, such as a desk or even the floor. Don’t put it on a carpeted surface, and don’t keep it inside a drawer or cabinet — you want cool air to be able to circulate around your computer. You need to give the hot air inside your PC somewhere to go as your fans spin to remove it.

Clean your fans and vents

A loud computer fan is often a dusty computer fan. As dust builds up, it prevents the fans from cooling your computer’s sensitive internal components as effectively as they should. Regularly remove dust from the fans and vents to allow your computer to cool itself efficiently.

Kindly follow all the methods and steps mentioned above and see if this works out or not. 

One of the reasons your computer won't boot but the fans spin could be a bad RAM. In this case, remove the RAM from its slot, then clean it and return it back to the same slot or try a different slot altogether. The best way to clear RAM is with a cloth and gently.

Regards,
J Wick