Mackbook won't switch to battery.

Hi everyone, I have a Macbook that had some water spilt into it. After drying it out it will only run from mains power. The moment i plug the charger in, it starts up and if it is knocked out it dies. I presume this is some kind of relay on the logic board that switches between mains and battery. The battery still charges and shows a full charge.
I just wondered if anyone knows how to fix this problem?
I have also tried changing the power management software as mentioned in another forum with no success.

Any ideas would be much appreciated

Many Thanks

Adam