broken keyless entry

i"m trying to figure out what has happened to my keyless entry. It started working intermittenly and has finally ceased to work at all. I have changed batteries in the fob, opened it up to have a look at the solders and they all look fine. The problem might be in the truck? Where is the "brain" or reciever for the keyless entry located? how can i test it?
Now that I think about it - my temp/compass guages have been inopperable for quite a while. any connection there?

I searched but this problem doesn't seem to be common so I found no good info.

thanks