Backlight always on when inverter changed

Hi, I changed the inverter on my macbook pro santa rosa (a1226) because there was no backlight anymore. Its a glossy screen and I put an inverter from the same model but from a mate screen. The problem is when I put the battery on, the screen is lighting.. when I power on the Mac book, it works well, I have my screen back but when I press light up or light down on the keyboard, it has no effect on the screen. What should I do ? I also change the inverter cable.