Green light will come on top screen flickers and turns off?

Check the lower LCD backlight cable and connection. It is under the large ribbon cable for the lower screen. You will need to unhook that cable. It is the small cable on the right under the larger video cable. The other small one is for the digitizer. Clean off any corrosion on the cable connector and cable. Make sure the cable is seated properly in the socket/connector and that the little brown retainer clip is pushed in holding the cable in. If the little brown retaining clip is missing you will need to replace it before it will work (you can find them on eBay). Reattach the large video cable. The thicker brown part of the cable should be just behind and parallel with the white line on the logic board. Make sure the flap retaining that cable in the socket is down evenly. Sometimes it wants to bow out in the center. Hold the battery firmly against the terminals. Press the power button. If the backlight for the lower screen is good the lower screen should at least flash if not stay on. If it doesn't replace the lower screen.