I just had a very similar problem. Display wouldnt come on at all, but before i got there, they said it was acting weird, dim, etc. I put a new board on, and got nothing. I put a new panel on and got nothing.. I started unplugging things on the board and found that the turbidity sensor had a short in it and it was causing the problem.
The turbidity sensor had shorted out their original board and my new board. I had to put a new sensor in, a second new board and the touch pad to get it to work.
try changing the sensor WPW10705575
after I put the sensor in, I had to replace the NEW board I had put in. apparently the sensor took it out as well...