Firewhat laptop are you using ?
what did you do to clean out the dust ? did you take the laptop apart and if yes, to what extent ?
I searched up a guide on how to clean the dust out of the inspiron 5720 http://blog.parts-people.com/2013/07/24/dell-inspiron-17r-5720-7720-cpu-cooling-fan-removal-and-installation/ this was the closest thing, I did exactly what they said, my best guess is that something else got accidently unplugged on the way, but I don't know where to look.