I read all the comments and thought I'd relate my son's problem with his 2008 Mac Pro.
He called one day almost in tears and said dad, my puter's broke.
It would not boot at all so I looked inside and what I saw reminded me of a battle zone.
-or maybe a zombie castle. Thick dust everywhere. Thick oily dust. Thick brown dust.
Hanging from everywhere and the fan blades coated with it. It covered the boards as well.
Nothing will work if dust connects all the transistors, etc.
You cannot totally clean something like that by blowing it out with those convenient cans of air.
Years ago I found a computer cleaning kit that hooks up to a vacuum hose. It's something every computer owner should have. It has several little vacuum brushes.
It took an hour to get all the dust vacuumed and the old Mac worked perfectly.
Here I have to add that my son is low on the list of tidiness. He will spend hours playing video games versus 5 minutes 'cleanup'. He smokes weed and the smoke being pulled through the fans is what gives the dust the oily brown color. His big spaniel keeps his small house full of dust. I advise any of you who know of a similar situation to inform that person to vacuum their computer at least every 4 months.
