Laptop fan comes on, screen stays black, fan shuts off and comes back next to again and then comp. shuts off...?

I took the pedestal off my laptop to check it out , reseated the ram and cleansed the fans. Everything looks ok under there. I position it all back together again and now...

once I turn it on, it powers up but the peak is black and the fans come connected, then they go around off, next they turn up again, and so my laptop shuts off.

What the euphemism is goin against? Someone have any ideas (other than effort someone else to do it)?