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My original assembly displays lcd broke as a result of a fall. Half of the screen is white. I bought the same model model computer for parts off of eBay and swapped out the assembly display. The issue is that if the computer shuts off it will only restart with the original assembly display connected. After it fully starts up I can switch to the new assembly display but not until then (or know this is not a good thing to do).
The battery is shot so the computer dies often. I’ve replaced the battery twice over the years but it’s ready to be replaced again. We only use it plugged it. Not sure if that has anything to do with it. MacBook Pro (15-inch, Mid 2009) 2.66 GHz intel core 2 Thank you in advance for any help!

I think you’re disconnecting and reconnecting the display while its turned on? Absolutely dont do that, inside the LVDS cable are 40 pins with ground, signal and power wires all next to each other. If the pins short you could see your connector set on fire and have a chain effect on the chips supplying those pins like the gpu. Also do you have a 9600m gt laptop?