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Hi! I unfortunately had some liquid damage on my MBP 13" 2009 keyboard. So I went ahead and watched some Youtube Videos on how to take it apart and clean it. The problem was, the backlight only worked on some keys in the center of the keyboard. I learned that the most common reason for this is improper alignment of the backlight. After hours and hours of trying to get it to work, I decided to trash the keyboard and get a replacement, since the keys were slightly worn out as well. I ordered the same keyboard number, installed it, but still the same problem. Every keyboard component is new and I took extra care when installing it, but no luck. I didnt find any threads on the internet where the problem still persisted after replacing the whole keyboard with the backlight. I also tried resetting the SMC. Here is a picture of the problem: http://imgur.com/HbWhWoF Any help would be very appreciated!

Try a new original backlight; the backlights which come combined with keyboards are copy ones and not original. They do not use the same material to evenly distribute the light across the keyboard, so pretty much all of them either just light the middle, or are brighter in certain areas (especially Retina Pro models, where it will be very bright at the top and very dim at the bottom). The LEDs on the older models are in the middle of the backlight, which would explain why all the light is in the middle of your keyboard and not spreading. Original new backlights will have white dots on the white material (compare to the original one), will have a RU sticker which peels off with the removable layer, and there will be blue tape for the adhesive around the side of the backlight, which will peel off in one piece, not multiple pieces like copies do. New originals are quite difficult to find for the older models, so it is usually best to get used original backlights, so you at least know it won’t have this issue. On the old non-Retina MacBooks, the keyboard backlight LEDs are either on or off; there is no “in between” where only some LEDs will light, unless the fault is with the keyboard backlight itself. The logic board just sends a voltage (KBDLED_ANODE) to 2 different pins of the backlight connector, which do the same thing. You can try plugging the backlight into the logic board loose to see if all the LEDs are lighting. On the newer Retina models, it is possible for some LEDs to not light, since they have 2 different cathode voltages, which cause the top row of LEDs to alternate on and off, but this is not possible on the older models unless it is a keyboard backlight issue, not logic board issue. In short, you have been sent a non-original backlight where none of them work as well as the originals in my experience. Get an original new/used backlight and try this since the LED light originates from the middle of the keyboard, and the layers in the backlight cause it to be distributed evenly across the keyboard. EDIT: what an original new backlight will look like https://www.aliexpress.com/item/Best-Qua…

The backlight is not on the keyboard itself its a piece that you order separately on Aliexpress or ebay

Some of the corrosion after a spill is so hard to find it’s almost impossible. We’ve had much better luck after getting an ultrasonic cleaner. We have been pulling boards out of machines we thought were toast (and had previously cleaned very well). I know these ultrasonic machines are expensive so you might contact a local repair place that has one and offer them $10-$20 to run it for you. I could save you the cost of a logic board. Transport the board in a static proof bag and keep your hubby fingers off of it ;-)