No video after replacing right fan

I replaced the right fan and attempted to get the logic board out to thoroughly clean the heat sink cooling grids. I unplugged the display cable. Now I am getting no display, the Apple on the back lights and I am getting a low glow on the display. When I use the power button to force shutdown, sometimes I will get a momentary bright white screen as the unit shuts down.

Prior to this I was having video issues and periodic log off or restarts leading me to feel it was a heat related problem. The display would develop green "halos" in background areas and during normal shutdown a "quivering" green screen. The left fan was replaced a couple of years ago when it completely quit.

Any thoughts?