Water damaged MacBook - no backlight?

The place to start is dealing with the liquid damage. If the residues from that aren't cleaned up you are going to chase ghost and really can't actually determine what if any parts are bad. Remove all power sources from your laptop. Push the power button for 10 seconds to help dissipate the capacitors. Then let it sit for an hour to ensure the capacitors have lost their charge. Remove the PRAM battery if it has one. Next remove your motherboard and clean both sides of it 90% or better rubbing alcohol or distilled water and a tooth brush. All are obtainable from your Pharmacy. Be liberal with the distilled water or alcohol let it flow underneath the chips to wash away what is under them, between pins etc... It is the contaminates in water (ionized minerals, which are salts) that are corrosive and conduct the electricity that do the damage, not the water itself. When you inspect your board you will see how small some of the components are and their connections/pins. Many of the IC pins you really can't inspect for corrosion between them without expensive optics. Flushing and brushing is the cheap and dirty way to remove those things you can't see with your naked eye. Dry it off with paper towels and let it sit for a day to dry the parts you can't reach, like under ICs. You can use a hair dryer on no heat or a fan to expedite drying, but still let it sit over night. My background is electronics. I am not an Apple guru. Reassemble your laptop give it a try. If this didn't solve your problem we'll work on getting the problem solved. You haven't stated your model number. If you would give us a model number along with the last 3 characters of your serial number we can point you to a guide to aide with motherboard removal and be better prepared to help you.