1 - 4 hours
The backlight on my Macbook A1181 suddenly went dark. For about a month, I could toggle the brightness buttons between dark and the lowest setting to keep the backlight on. Eventually it became more and more difficult to keep the light on and I would have to toggle the brightness buttons every few minutes or more. The light would also go out with any slight movement of the screen. There was no particular angle that caused the problem but if the light was on, any movement would turn it off. It always worked just fine hooked up to an external display and I could use a flashlight held up to the screen and see the computer functioning properly just without the backlight.
The repair went well and a new LCD screen fixed the problem. However before trying the screen I also replaced the inverter card and inverter cable which did not fix the problem.
I printed the IFix it guide which was very helpful and taped the screws on each relevant page to keep them in order. According to my research, this problem can sometimes be caused by either the inverter card or cable but be aware that I wasted $70 replacing those and eventually had to replace the entire LCD. It was difficult to trouble shoot beyond those 3 parts so I would probably try the same repairs in order again since it was easier and cheaper to begin with the inverter card and cable first.