From your question update I understand that the macbook GPU is good and you get video on internal and external screens but no lightning on the internal. This often a problem with liquid spilled on this macbook model. You should carefully clean the LVDS socket that brings video and lightning to the LCD screen. Check for socket internal discoloration like black spots or corrosion. Clean it with a tooth brush and 90% isopropyl alcohol. Check also the LVDS cable connector which may need to be cleaned too.
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From your question update I understand that the macbook GPU is good and you get video on internal and external screens but no lightning on the internal. This is often a problem caused by liquid spilled on this macbook model. You should carefully clean the LVDS socket that brings video and lightning to the LCD screen. Check for socket internal discoloration like black spots or corrosion. Clean it with a tooth brush and 90% isopropyl alcohol. Check also the LVDS cable connector which may need to be cleaned too.
From your question update I understand that the macbook GPU is good and you get video on internal and external screens but no lightning on the internal. This often a problem with liquid spilled on this macbook model. You should carefully clean the LVDS socket that brings video and lightning to the LCD screen. Check for socket internal discoloration like black spots or corrosion. Clean it with a tooth brush and 90% isopropyl alcohol. Check also the LVDS cable connector which may need to be cleaned too.