Whenever you have an electric problem, you need to follow the same procedure: get a tester bulb or multi-meter and trace the power all the way to the device which you think is not working. You should test first at the screen power plugs and see if they are getting 12V. Then move along the power line, I guess next to the fuse and check both blades, then the relay that is supposed to power the units, etc.
Having a FSM would help immensely, google where you can download one. I have downloaded mine long time ago and do not remember from where.
Hoping that helps!