Replaced Macbook Screen

[HugoM]

I recently shattered my macbook screen. I quickly ordered a replacement screen and installed it. However, when I boot up there is no video and the backlight doesn't come on. The screen works fine on an old dell laptop. The old screen works.

I fiddled around for a bit and once I managed to get video, I was then able to go into system preferences and click in the brightness slider and suddenly the backlight, worked perfectly, but once I reset the computer I was back to my original problem.

The only way I can get it to work is to plug the backlight into the new screen and video into the old, doing this makes the backlight come on on the new screen on video on the old. Once the computer's booted if I swap the video from the old screen to the new then I can get the new one working - however my computer thinks the old screen is still connected.

By plugging the computer into an external screen and booting with the new screen I can see that in system profiler the new screen isn't listed.

Does anyone have any idea?

Thanks.